orbital alignment dependence: Topics by Science.gov

Sample records for orbital alignment dependence

Orbital Verification of the CXO High-Resolution Mirror Assembly Alignment and Vignetting

NASA Technical Reports Server (NTRS)

Gaetz, T. J.; Jerius, D.; Edgar, R. J.; VanSpeybroeck, L. P.; Schwartz, D. A.; Markevitch, M.; Schulz, N. S.

2000-01-01

Prior to launch, the High Resolution Mirror Assembly (HRMA) of the Chandra X-ray Observatory underwent extensive ground testing at the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville. Observations made during the post-launch Orbital Activation and Calibration period, allow the on-orbit condition of the X-ray optics to be assessed. Based on these ground-based and on-orbit data, we examine the alignment of the x-ray optics based on the PSF, and the boresight and alignment of the optical axis alignment relative to the detectors. We examine the vignetting and the single reflection ghost suppression properties of the telescope. Slight imperfections in alignment lead to a small azimuthal dependence of the off-axis area; the morphology of off-axis images also shows an additional small azimuthal dependence varying as 1/2 the off-axis azimuth angle.
Dependence of field-aligned electron precipitation on season, altitude and pitch angle

NASA Technical Reports Server (NTRS)

Berko, F. W.; Hoffman, R. A.

1973-01-01

The occurrence of field-aligned 2.3 keV electron precipitation was examined by using data from more than 7500 orbits of the polar-orbiting satellite, OGO-4. The frequency of occurrence of field aligned precipitation was highest at actual pitch angles between 7 and 10 deg, being highest in the winter months, at highest satellite altitudes. Acceleration by a localized parallel electric field established by electrostatic charge layers is proposed to explain particle observations.
Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

NASA Astrophysics Data System (ADS)

L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

2017-04-01

We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).
Polar alignment of a protoplanetary disc around an eccentric binary II: Effect of binary and disc parameters

NASA Astrophysics Data System (ADS)

Martin, Rebecca G.; Lubow, Stephen H.

2018-06-01

In a recent paper Martin & Lubow showed that a circumbinary disc around an eccentric binary can undergo damped nodal oscillations that lead to the polar (perpendicular) alignment of the disc relative to the binary orbit. The disc angular momentum vector aligns to the eccentricity vector of the binary. We explore the robustness of this mechanism for a low mass disc (0.001 of the binary mass) and its dependence on system parameters by means of hydrodynamic disc simulations. We describe how the evolution depends upon the disc viscosity, temperature, size, binary mass ratio, orbital eccentricity and inclination. We compare results with predictions of linear theory. We show that polar alignment of a low mass disc may occur over a wide range of binary-disc parameters. We discuss the application of our results to the formation of planetary systems around eccentric binary stars.
The Generation of the Distant Kuiper Belt by Planet Nine from an Initially Broad Perihelion Distribution

NASA Astrophysics Data System (ADS)

Khain, Tali; Batygin, Konstantin; Brown, Michael E.

2018-04-01

The observation that the orbits of long-period Kuiper Belt objects are anomalously clustered in physical space has recently prompted the Planet Nine hypothesis - the proposed existence of a distant and eccentric planetary member of our Solar System. Within the framework of this model, a Neptune-like perturber sculpts the orbital distribution of distant Kuiper Belt objects through a complex interplay of resonant and secular effects, such that the surviving orbits get organized into apsidally aligned and anti-aligned configurations with respect to Planet Nine's orbit. We present results on the role of Kuiper Belt initial conditions on the evolution of the outer Solar System using numerical simulations. Intriguingly, we find that the final perihelion distance distribution depends strongly on the primordial state of the system, and demonstrate that a bimodal structure corresponding to the existence of both aligned and anti-aligned clusters is only reproduced if the initial perihelion distribution is assumed to extend well beyond 36 AU. The bimodality in the final perihelion distance distribution is due to the permanently stable objects, with the lower perihelion peak corresponding to the anti-aligned orbits and the higher perihelion peak corresponding to the aligned orbits. We identify the mechanisms that enable the persistent stability of these objects and locate the regions of phase space in which they reside. The obtained results contextualize the Planet Nine hypothesis within the broader narrative of solar system formation, and offer further insight into the observational search for Planet Nine.
The Generation of the Distant Kuiper Belt by Planet Nine from an Initially Broad Perihelion Distribution

NASA Astrophysics Data System (ADS)

Khain, Tali; Batygin, Konstantin; Brown, Michael E.

2018-06-01

The observation that the orbits of long-period Kuiper Belt objects (KBOs) are anomalously clustered in physical space has recently prompted the Planet Nine hypothesis—the proposed existence of a distant and eccentric planetary member of our solar system. Within the framework of this model, a Neptune-like perturber sculpts the orbital distribution of distant KBOs through a complex interplay of resonant and secular effects, such that in addition to perihelion-circulating objects, the surviving orbits get organized into apsidally aligned and anti-aligned configurations with respect to Planet Nine’s orbit. In this work, we investigate the role of Kuiper Belt initial conditions on the evolution of the outer solar system using numerical simulations. Intriguingly, we find that the final perihelion distance distribution depends strongly on the primordial state of the system, and we demonstrate that a bimodal structure corresponding to the existence of both aligned and anti-aligned clusters is only reproduced if the initial perihelion distribution is assumed to extend well beyond ∼36 au. The bimodality in the final perihelion distance distribution is due to the existence of permanently stable objects, with the lower perihelion peak corresponding to the anti-aligned orbits and the higher perihelion peak corresponding to the aligned orbits. We identify the mechanisms that enable the persistent stability of these objects and locate the regions of phase space in which they reside. The obtained results contextualize the Planet Nine hypothesis within the broader narrative of solar system formation and offer further insight into the observational search for Planet Nine.
Orbitally dependent kinetic exchange in a heterobimetallic pair: Ferromagnetic spin alignment and magnetic anisotropy in the cyano-bridged Cr(III)Fe(II) dimer

NASA Astrophysics Data System (ADS)

Palii, A. V.; Tsukerblat, B. S.; Verdaguer, M.

2002-11-01

The problem of the kinetic exchange interaction in the cyanide-bridged heterobinuclear dimers involving orbitally degenerate transition metal ions is considered. The developed approach is based on the concept of the effective Hamiltonian of the orbitally dependent kinetic exchange. We deduce this many-electron Hamiltonian on the microscopic background so that all relevant biorbital transfer processes are taken into account as well as the properties of the many-electron states. The bioctahedral cyanide-bridged Cr(III)Fe(II) dimer is considered in detail as an example distinctly exhibiting new quantitative and qualitative features of the orbitally dependent exchange and as a structural unit of three-dimensional ferromagnetic crystals {Fe(II)3)Cr(III)(CN62}[middle dot]13H2O. The proposed mechanism of the kinetic exchange involves the electron transfer from the double occupied t2 orbitals of Fe(II) [ground state 5T2(t2)4e2] to the half occupied t2 orbitals of Cr(III) [ground state 4A2(t2)3] resulting in the charge transfer state 3T1(t2)4Cr(II)- 6A1(t2)3e2 Fe(III) and the transfer between the half-occupied t2 orbitals of the metal ions resulting in the charge transfer state 3T1(t2)4Cr(II)- 4T2(t2)3e2 Fe(III). The effective Hamiltonian of the orbitally dependent exchange for the Cr(III)Fe(II) pair deduced within this theoretical framework describes competitive ferro- and antiferromagnetic contributions arising from these two charge transfer states. This Hamiltonian leads to a complex energy pattern, consisting of two interpenetrating Heisenberg-like schemes, one exhibiting ferromagnetic and another one antiferromagnetic splitting. The condition for the ferromagnetic spin alignment in the ground state is deduced. The orbitally dependent terms of the Hamiltonian are shown to give rise to a strong magnetic anisotropy of the system, this result as well as the condition for the spin alignment in the ground term are shown to be out of the scope of the Goodenough-Kanamori rules. Along with the full spin S the energy levels are labeled by the orbital quantum numbers providing thus the direct information about the magnetic anisotropy of the system. Under a reasonable estimation of the excitation energies based on the optical absorption data we conclude that the kinetic exchange in the cyanide-bridged Cr(III)Fe(II) pair leads to the ferromagnetic spin alignment exhibiting at the same time strong axial magnetic anisotropy with C4 easy axis of magnetization.
IUS prerelease alignment

NASA Technical Reports Server (NTRS)

Evans, F. A.

1978-01-01

Space shuttle orbiter/IUS alignment transfer was evaluated. Although the orbiter alignment accuracy was originally believed to be the major contributor to the overall alignment transfer error, it was shown that orbiter alignment accuracy is not a factor affecting IUS alignment accuracy, if certain procedures are followed. Results are reported of alignment transfer accuracy analysis.
Orbit Alignment in Triple Stars

NASA Astrophysics Data System (ADS)

Tokovinin, Andrei

2017-08-01

The statistics of the angle Φ between orbital angular momenta in hierarchical triple systems with known inner visual or astrometric orbits are studied. A correlation between apparent revolution directions proves the partial orbit alignment known from earlier works. The alignment is strong in triples with outer projected separation less than ˜50 au, where the average Φ is about 20^\\circ . In contrast, outer orbits wider than 1000 au are not aligned with the inner orbits. It is established that the orbit alignment decreases with the increasing mass of the primary component. The average eccentricity of inner orbits in well-aligned triples is smaller than in randomly aligned ones. These findings highlight the role of dissipative interactions with gas in defining the orbital architecture of low-mass triple systems. On the other hand, chaotic dynamics apparently played a role in shaping more massive hierarchies. The analysis of projected configurations and triples with known inner and outer orbits indicates that the distribution of Φ is likely bimodal, where 80% of triples have {{Φ }}< 70^\\circ and the remaining ones are randomly aligned.
KOI2138 -- a Spin-Orbit Aligned Intermediate Period Super-Earth

NASA Astrophysics Data System (ADS)

Barnes, Jason W.

2015-11-01

A planet's formation and evolution are encoded in spin-orbit alignment -- the planet's inclination relative to its star's equatorial plane. While the solar system's spin-orbit aligned planets indicate our own relatively quiescent history, many close-in giant planets show significant misalignment. Some planets even orbit retrograde! Hot Jupiters, then, have experienced fundamentally different histories than we experienced here in the solar system. In this presentation, I will show a new determination of the spin-orbit alignment of 2.1 REarth exoplanet candidate KOI2138. KOI2138 shows a gravity-darkened transit lightcurve that is consistent with spin-orbit alignment. This measurement is important because the only other super-Earth with an alignment determination (55 Cnc e, orbit period 0.74 days) is misaligned. With an orbital period of 23.55 days, KOI2138 is far enough from its star to avoid tidal orbit evolution. Therefore its orbit is likely primordial, and hence it may represent the tip of an iceberg of terrestrial, spin-orbit aligned planets that have histories that more closely resemble that of the solar system's terrestrial planets.
Atomic alignment effect in the dissociative energy transfer reaction of metal carbonyls (Fe(CO)5, Ni(CO)4) with oriented Ar (3P2, M(J) = 2).

PubMed

Ohoyama, H; Matsuura, Y

2011-10-13

The atomic alignment effect has been studied for the dissociative energy transfer reaction of metal carbonyls (Fe(CO)(5), Ni(CO)(4)) with the oriented Ar ((3)P(2), M(J) = 2). The emission intensity from the excited metal products (Fe*, Ni*) has been measured as a function of the atomic alignment in the collision frame. The selectivity of the atomic orbital alignment of Ar ((3)P(2), M(J) = 2) (rank 2 moment, a(2)) is found to be opposite for the two reaction systems; the Fe(CO)(5) reaction is favorable at the Π configuration (positive a(2)), while the Ni(CO)(4) reaction is favorable at the Σ configuration (negative a(2)). Moreover, a significant spin alignment effect (rank 4 moment, a(4)) is recognized only in the Ni(CO)(4) reaction. The atomic alignment effect turns out to be essentially different between the two reaction systems; the Fe(CO)(5) reaction is controlled by the configuration of the half-filled 3p atomic orbital of Ar ((3)P(2)) in the collision frame (L dependence), whereas the Ni(CO)(4) reaction is controlled by the configuration of the total angular moment J (including spin) of Ar ((3)P(2)) in the collision frame (J dependence). As the origin of J dependence observed only in the Ni(CO)(4) reaction, the correlation (and/or the interference) between two electron exchange processes via the electron rearrangements is proposed.
ϕ Meson Spin Alignment and the Azimuthal Angle Dependence of Λ (Λ) Polarization in Au+Au collisions at RHIC

NASA Astrophysics Data System (ADS)

Tu, Biao

2018-02-01

Initial large global angular momentum in non-central relativistic heavy-ion collisions can produce strong vorticity, and through the spin-orbit coupling, causes the spin of particles to align with the system's global angular momentum. We present the azimuthal angle dependent (relative to the reaction plane) polarization for Λ and Λ in mid-central Au+Au collisions at = 200 GeV. We also present the ϕ meson spin alignment parameter, ρ00 in Au+Au collisions at = 19.6, 27, 39, 62.4 and 200 GeV. The implications of the results are discussed.
Internuclear separation dependent ionization of the valence orbitals of I2 by strong laser fields.

PubMed

Chen, H; Tagliamonti, V; Gibson, G N

2012-11-09

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σ(g)(2)π(u)(4)π(g)(4)σ(u)(0). We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σ(g)) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.
Internuclear Separation Dependent Ionization of the Valence Orbitals of I2 by Strong Laser Fields

NASA Astrophysics Data System (ADS)

Chen, H.; Tagliamonti, V.; Gibson, G. N.

2012-11-01

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σg2πu4πg4σu0. We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σg) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.
Relative properties of smooth terminating bands

NASA Astrophysics Data System (ADS)

Afanasjev, A. V.; Ragnarsson, I.

1998-01-01

The relative properties of smooth terminating bands observed in the A ∼ 110 mass region are studied within the effective alignment approach. Theoretical values of ietf are calculated using the configuration-dependent shell-correction model with the cranked Nilsson potential. Reasonable agreement with experiment shows that previous interpretations of these bands are consistent with the present study. Contrary to the case of superdeformed bands, the effective alignments of these bands deviate significantly from the pure single-particle alignments of the corresponding orbitals. This indicates that in the case of smooth terminating bands, the effects associated with changes in equilibrium deformations contribute significantly to the effective alignment.
Thermoelectricity in fullerene-metal heterojunctions.

PubMed

Yee, Shannon K; Malen, Jonathan A; Majumdar, Arun; Segalman, Rachel A

2011-10-12

Thermoelectricty in heterojunctions, where a single-molecule is trapped between metal electrodes, has been used to understand transport properties at organic-inorganic interfaces. (1) The transport in these systems is highly dependent on the energy level alignment between the molecular orbitals and the Fermi level (or work function) of the metal contacts. To date, the majority of single-molecule measurements have focused on simple small molecules where transport is dominated through the highest occupied molecular orbital. (2, 3) In these systems, energy level alignment is limited by the absence of electrode materials with low Fermi levels (i.e., large work functions). Alternatively, more controllable alignment between molecular orbitals and the Fermi level can be achieved with molecules whose transport is dominated by the lowest unoccupied molecular orbital (LUMO) because of readily available metals with lower work functions. Herein, we report molecular junction thermoelectric measurements of fullerene molecules (i.e., C(60), PCBM, and C(70)) trapped between metallic electrodes (i.e., Pt, Au, Ag). Fullerene junctions demonstrate the first strongly n-type molecular thermopower corresponding to transport through the LUMO, and the highest measured magnitude of molecular thermopower to date. While the electronic conductance of fullerenes is highly variable, due to fullerene's variable bonding geometries with the electrodes, the thermopower shows predictable trends based on the alignment of the LUMO with the work function of the electrodes. Both the magnitude and trend of the thermopower suggest that heterostructuring organic and inorganic materials at the nanoscale can further enhance thermoelectric performance, therein providing a new pathway for designing thermoelectric materials.
Field-aligned currents and magnetospheric convection - A comparison between MHD simulations and observations

NASA Technical Reports Server (NTRS)

Walker, Raymond J.; Ogino, Tatsuki

1988-01-01

A time-dependent three-dimensional MHD model was used to investigate the magnetospheric configuration as a function of the interplanetary magnetic field direction when it was in the y-z plane in geocentric solar magnetospheric coordinates. The model results show large global convection cells, tail lobe cells, high-latitude polarcap cells, and low latitude cells. The field-aligned currents generated in the model magnetosphere and the model convection system are compared with observations from low-altitude polar orbiting satellites.
Optical control of ground-state atomic orbital alignment: Cl(2P3/2) atoms from HCl(v=2,J=1) photodissociation.

PubMed

Sofikitis, Dimitris; Rubio-Lago, Luis; Martin, Marion R; Ankeny Brown, Davida J; Bartlett, Nathaniel C-M; Alexander, Andrew J; Zare, Richard N; Rakitzis, T Peter

2007-10-14

H(35)Cl(v=0,J=0) molecules in a supersonic expansion were excited to the H(35)Cl(v=2,J=1,M=0) state with linearly polarized laser pulses at about 1.7 microm. These rotationally aligned J=1 molecules were then selectively photodissociated with a linearly polarized laser pulse at 220 nm after a time delay, and the velocity-dependent alignment of the (35)Cl((2)P(32)) photofragments was measured using 2+1 REMPI and time-of-flight mass spectrometry. The (35)Cl((2)P(32)) atoms are aligned by two mechanisms: (1) the time-dependent transfer of rotational polarization of the H(35)Cl(v=2,J=1,M=0) molecule to the (35)Cl((2)P(32)) nuclear spin [which is conserved during the photodissociation and thus contributes to the total (35)Cl((2)P(32)) photofragment atomic polarization] and (2) the alignment of the (35)Cl((2)P(32)) electronic polarization resulting from the photoexcitation and dissociation process. The total alignment of the (35)Cl((2)P(32)) photofragments from these two mechanisms was found to vary as a function of time delay between the excitation and the photolysis laser pulses, in agreement with theoretical predictions. We show that the alignment of the ground-state (35)Cl((2)P(32)) atoms, with respect to the photodissociation recoil direction, can be controlled optically. Potential applications include the study of alignment-dependent collision effects.
X-ray microprobe of orbital alignment in strong-field ionized atoms.

PubMed

Young, L; Arms, D A; Dufresne, E M; Dunford, R W; Ederer, D L; Höhr, C; Kanter, E P; Krässig, B; Landahl, E C; Peterson, E R; Rudati, J; Santra, R; Southworth, S H

2006-08-25

We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems.
Molecular orbital imaging via above-threshold ionization with circularly polarized pulses.

PubMed

Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lu, Peixiang; Xu, Zhizhan

2011-07-18

Above-threshold ionization (ATI) for aligned or orientated linear molecules by circularly polarized laser pulsed is investigated. It is found that the all-round structural information of the molecular orbital is extracted with only one shot by the circularly polarized probe pulse rather than with multi-shot detections in a linearly polarized case. The obtained photoelectron momentum spectrum directly depicts the symmetry and electron distribution of the occupied molecular orbital, which results from the strong sensitivity of the ionization probability to these structural features. Our investigation indicates that the circularly polarized probe scheme would present a simple method to study the angle-dependent ionization and image the occupied electronic orbital.

Experience from the in-flight calibration of the Extreme Ultraviolet Explorer (EUVE) and Upper Atmosphere Research Satellite (UARS) fixed head star trackers (FHSTs)

NASA Technical Reports Server (NTRS)

Lee, Michael

1995-01-01

Since the original post-launch calibration of the FHSTs (Fixed Head Star Trackers) on EUVE (Extreme Ultraviolet Explorer) and UARS (Upper Atmosphere Research Satellite), the Flight Dynamics task has continued to analyze the FHST performance. The algorithm used for inflight alignment of spacecraft sensors is described and the equations for the errors in the relative alignment for the simple 2 star tracker case are shown. Simulated data and real data are used to compute the covariance of the relative alignment errors. Several methods for correcting the alignment are compared and results analyzed. The specific problems seen on orbit with UARS and EUVE are then discussed. UARS has experienced anomalous tracker performance on an FHST resulting in continuous variation in apparent tracker alignment. On EUVE, the FHST residuals from the attitude determination algorithm showed a dependence on the direction of roll during survey mode. This dependence is traced back to time tagging errors and the original post launch alignment is found to be in error due to the impact of the time tagging errors on the alignment algorithm. The methods used by the FDF (Flight Dynamics Facility) to correct for these problems is described.
Atomic alignment effect on reactivity and on product alignment in the energy-transfer reaction of oriented Ar (3P2, 4s [3/2]2, M(J) = 2) + Kr (4p6, 1S0) → Ar (3p6, 1S0) + Kr (5p [3/2]2).

PubMed

Ohoyama, H

2015-03-12

Steric effect for the formation of Kr (5p [3/2]₂) in the energy transfer reaction of Ar (³P₂, 4s [3/2]₂) + Kr has been studied by using an oriented Ar (³P₂, 4s [3/2]₂, M(J) = 2) beam at a collision energy of ∼0.09 eV. The emission intensity of Kr (5p [3/2]₂) is ca. 2 times enhanced when the angular momentum (J(Ar)) of Ar (³P₂) is aligned perpendicular to the relative velocity vector (v(R)). In addition, the Kr (5p [3/2]₂) emission is highly polarized parallel to v(R) (I(∥)/I(⊥) ∼ 1.2) when JAr is aligned perpendicular to v(R). The observed polarization moments indicate that the alignment of the unpaired Ar (3p) orbital of Ar (³P₂) to v(R), (Σ (|L′| = 0), Π (|L′| = 1)), dominates the energy transfer probability (σ(Π)(∥): σ(Σ)(∥): σ(Π)(⊥): σ(Σ)(⊥) = 0.49:1.33:0.55:1.23) and also the alignment of the Kr (5p) orbital of Kr (5p [3/2]₂) to v(R): the Σ-configuration of the Ar (3p) orbital leads to the parallel alignment (Σ-configuration) of the Kr(5p) orbital to v(R), conversely, the Π-configuration of Ar (3p) orbital leads to the perpendicular alignment (Π-configuration) of the Kr(5p) orbital. In addition, the selectivity of the alignment of the Kr (5p) orbital turns out to vary from perpendicular to parallel as the collision energy increases after a threshold down to 0.03 eV.
High Gain Antenna Calibration on Three Spacecraft

NASA Technical Reports Server (NTRS)

Hashmall, Joseph A.

2011-01-01

This paper describes the alignment calibration of spacecraft High Gain Antennas (HGAs) for three missions. For two of the missions (the Lunar Reconnaissance Orbiter and the Solar Dynamics Observatory) the calibration was performed on orbit. For the third mission (the Global Precipitation Measurement core satellite) ground simulation of the calibration was performed in a calibration feasibility study. These three satellites provide a range of calibration situations-Lunar orbit transmitting to a ground antenna for LRO, geosynchronous orbit transmitting to a ground antenna fer SDO, and low Earth orbit transmitting to TDRS satellites for GPM The calibration results depend strongly on the quality and quantity of calibration data. With insufficient data the calibration Junction may give erroneous solutions. Manual intervention in the calibration allowed reliable parameters to be generated for all three missions.
Determination of structure parameters in strong-field tunneling ionization theory of molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Songfeng; Jin Cheng; College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou, Gansu 730070

2010-03-15

In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wave function of the molecular orbital from which the electron is removed. The orbital wave functions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory. We show that the asymptotic wave function can be improved with an iteration method and after one iteration accurate asymptotic wave functions and structure parameters are determined. Withmore » the new parameters we examine the alignment-dependent tunneling ionization probabilities for several molecules and compare with other calculations and with recent measurements, including ionization from inner molecular orbitals.« less
Study of an orbiting tethered dumbbell system having positive orbital energy

NASA Technical Reports Server (NTRS)

Arnold, David A.

1988-01-01

For very long tethered systems the sum of the kinetic and potential energy can be positive. The system remains in a circular orbit as long as the masses remain vertically aligned. The system is unstable without constant control of the alignment. If the upper mass rotates forward in the direction of the orbital motion, the system escapes out of orbit. If the upper mass rotates backward, the system falls out of orbit and the lower mass impacts the body around which the system is orbiting.
THE BANANA PROJECT. IV. TWO ALIGNED STELLAR ROTATION AXES IN THE YOUNG ECCENTRIC BINARY SYSTEM EP CRUCIS: PRIMORDIAL ORIENTATION AND TIDAL ALIGNMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albrecht, Simon; Winn, Joshua N.; Setiawan, Johny

With observations of the EP Cru system, we continue our series of measurements of spin-orbit angles in eclipsing binary star systems, the BANANA project (Binaries Are Not Always Neatly Aligned). We find a close alignment between the sky projections of the rotational and orbital angular momentum vectors for both stars ({beta}{sub p} = -1. Degree-Sign 8 {+-} 1. Degree-Sign 6 and |{beta}{sub s}| < 17 Degree-Sign ). We also derive precise absolute dimensions and stellar ages for this system. The EP Cru and DI Her systems provide an interesting comparison: they have similar stellar types and orbital properties, but DImore » Her is younger and has major spin-orbit misalignments, raising the question of whether EP Cru also had a large misalignment at an earlier phase of evolution. We show that tidal dissipation is an unlikely explanation for the good alignment observed today, because realignment happens on the same timescale as spin-orbit synchronization, and the stars in EP Cru are far from synchronization (they are spinning nine times too quickly). Therefore it seems that some binaries form with aligned axes, while other superficially similar binaries are formed with misaligned axes.« less
Targetting and guidance program documentation. [a user's manual

NASA Technical Reports Server (NTRS)

Harrold, E. F.; Neyhard, J. F.

1974-01-01

A FORTRAN computer program was developed which automatically targets two and three burn rendezvous missions and performs feedback guidance using the GUIDE algorithm. The program was designed to accept a large class of orbit specifications and to automatically choose a two or three burn mission depending upon the time alignment of the vehicle and target. The orbits may be specified as any combination of circular and elliptical orbits and may be coplanar or inclined, but must be aligned coaxially with their perigees in the same direction. The program accomplishes the required targeting by repeatedly converging successively more complex missions. It solves the coplanar impulsive version of the mission, then the finite burn coplanar mission, and finally, the full plane change mission. The GUIDE algorithm is exercised in a feedback guidance mode by taking the targeted solution and moving the vehicle state step by step ahead in time, adding acceleration and navigational errors, and reconverging from the perturbed states at fixed guidance update intervals. A program overview is presented, along with a user's guide which details input, output, and the various subroutines.
Tracking spin-axis orbital alignment in selected binary systems: the Torun Rossiter-McLaughlin effect survey

NASA Astrophysics Data System (ADS)

Sybilski, P.; Pawłaszek, R. K.; Sybilska, A.; Konacki, M.; Hełminiak, K. G.; Kozłowski, S. K.; Ratajczak, M.

2018-07-01

We have obtained high-resolution spectra of four eclipsing binary systems (FM Leo, NN Del, V963 Cen and AI Phe) with the view to gaining an insight into the relative orientations of their stellar spin axes and orbital axes. The so-called Rossiter-McLaughlin (RM) effect, i.e. the fact that the broadening and the amount of blue or redshift in the spectra during an eclipse depends on the tilt of the spin axis of the background star, has the potential of reconciling observations and theoretical models if such a tilt is found. We analyse the RM effect by disentangling the spectra, removing the front component and measuring the remaining, distorted lines with a broadening function (BF) obtained from single-value decomposition (SVD), weighting by the intensity centre of the BF in the eclipse. All but one of our objects show no significant misalignment, suggesting that aligned systems are dominant. We provide stellar as well as orbital parameters for our systems. With five measured spin-orbit angles, we increase significantly (from 9 to 14) the number of stars for which it has been measured. The spin-orbit angle β calculated for AI Phe's secondary component shows a misalignment of 87±17°. NN Del, with a large separation of components and a long dynamical time-scale for circularization and synchronization, is an example of a close to primordial spin-orbit angle measurement.
Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices.

PubMed

Yang, Qing-Dan; Li, Ho-Wa; Cheng, Yuanhang; Guan, Zhiqiang; Liu, Taili; Ng, Tsz-Wai; Lee, Chun-Sing; Tsang, Sai-Wing

2016-03-23

Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy. Using this approach, we find that some of the BHJ blends simply follow vacuum level alignment, but others show strong energy level shifting as a result of Fermi level pinning. Independently, by measuring the temperature-dependent open-circuit voltage (VOC), we find that the effective energy gap (Eeff), the energy difference between the highest occupied molecular orbital of the polymer donor (EHOMO-D) and lowest unoccupied molecular orbital of the PCBM acceptor (ELUMO-A), obtained by photoemission spectroscopy in all polymer:PCBM blends has an excellent agreement with the extrapolated VOC at 0 K. Consequently, the photovoltage loss of various organic BHJ photovoltaic devices at room temperature is in a range of 0.3-0.6 V. It is believed that the demonstrated direct measurement approach of the energy level alignment in solution-processed organic BHJ will bring deeper insight into the origin of the VOC and the corresponding photovoltage loss mechanism in organic photovoltaic cells.
Understanding the electronic structure of CdSe quantum dot-fullerene (C{sub 60}) hybrid nanostructure for photovoltaic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Sunandan; Rajbanshi, Biplab; Sarkar, Pranab, E-mail: pranab.sarkar@visva-bharati.ac.in

2014-09-21

By using the density-functional tight binding method, we studied the electronic structure of CdSe quantum dot(QD)-buckminsterfullerene (C{sub 60}) hybrid systems as a function of both the size of the QD and concentration of the fullerene molecule. Our calculation reveals that the lowest unoccupied molecular orbital energy level of the hybrid CdSeQD-C{sub 60} systems lies on the fullerene moiety, whereas the highest occupied molecular orbital (HOMO) energy level lies either on the QD or the fullerene depending on size of the CdSe QD. We explored the possibility of engineering the energy level alignment by varying the size of the CdSe QD.more » With increase in size of the QD, the HOMO level is shifted upward and crosses the HOMO level of the C{sub 60}-thiol molecule resulting transition from the type-I to type-II band energy alignment. The density of states and charge density plot support these types of band gap engineering of the CdSe-C{sub 60} hybrid systems. This type II band alignment indicates the possibility of application of this nanohybrid for photovoltaic purpose.« less
Light control of orbital domains: case of the prototypical manganite La0.5Sr1.5MnO4

NASA Astrophysics Data System (ADS)

Miller, Timothy; Gensch, Michael; Wall, Simon

2016-12-01

Control of electronic and structural ordering in correlated materials on the ultrafast timescale with light is a new and emerging approach to disentangle the complex interplay of the charge, spin, orbital and structural degree of freedom. In this paper we present an overview of how orbital order and orbital domains can be controlled by near IR and THz radiation in the layered manganite La0.5Sr1.5MnO4. We show how near-IR pumping can efficiently and rapidly melt orbital ordering. However, the nanoscale domain structure recovers unchanged demonstrating the importance of structural defects for the orbital domain formation. On the contrary, we show that pulsed THz fields can be used to effectively orientate the domains. In this case the alignment depends on the in-plane electric field polarisation and is induced by an energy penalty that arises from THz field induced hopping of the localised charges.
A spin-orbit alignment for the hot Jupiter HATS-3b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Addison, B. C.; Tinney, C. G.; Wright, D. J.

We have measured the alignment between the orbit of HATS-3b (a recently discovered, slightly inflated Hot Jupiter) and the spin axis of its host star. Data were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous calibration system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The sky-projected spin-orbit angle of λ = 3° ± 25° was determined from spectroscopic measurements of the Rossiter-McLaughlin effect. This is the first exoplanet discovered through the HATSouth transit survey to have its spin-orbit angle measured. Our results indicate that the orbital plane of HATS-3b is consistent with being aligned to the spin axismore » of its host star. The low obliquity of the HATS-3 system, which has a relatively hot mid F-type host star, agrees with the general trend observed for Hot Jupiter host stars with effective temperatures >6250 K to have randomly distributed spin-orbit angles.« less
Building up the spin - orbit alignment of interacting galaxy pairs

NASA Astrophysics Data System (ADS)

Moon, Jun-Sung; Yoon, Suk-Jin

2018-01-01

Galaxies are not just randomly distributed throughout space. Instead, they are in alignment over a wide range of scales from the cosmic web down to a pair of galaxies. Motivated by recent findings that the spin and the orbital angular momentum vectors of galaxy pairs tend to be parallel, we here investigate the spin - orbit orientation in close pairs using the Illustris cosmological simulation. We find that since z ~ 1, the parallel alignment has become progressively stronger with time through repetitive encounters. The pair Interactions are preferentially in prograde at z = 0 (over 5 sigma significance). The prograde fraction at z = 0 is larger for the pairs influenced more heavily by each other during their evolution. We find no correlation between the spin - orbit orientation and the surrounding large-scale structure. Our results favor the scenario in which the alignment in close pairs is caused by tidal interactions later on, rather than the primordial torquing by the large-scale structures.
Angular and Intensity Dependent Spectral Modulations in High Harmonics from N2

NASA Astrophysics Data System (ADS)

McFarland, Brian; Farrell, Joseph; Bucksbaum, Philip; Guehr, Markus

2009-05-01

The spectral amplitude and phase modulation of high harmonics (HHG) in molecules provides important clues to molecular structure and dynamics in strong laser fields. We have studied these effects in aligned N2. Earlier results of HHG experiments claimed that the spectral amplitude modulation was predominantly due to geometrical interference between the recombining electron and the highest occupied molecular orbital (HOMO) [1]. We report evidence that contradicts this simple view. We observe a phase jump accompanied by a spectral minimum for HHG in aligned N2. The minimum shifts to lower harmonics as the angle between the molecular axis and harmonic generation polarization increases, and shifts to higher harmonics with increasing harmonic generation intensity. The features observed cannot be fully explained by a geometrical model. We discuss alternative explanations involving multi orbital effects [2]. [0pt] [1] Lein et al., Phys. Rev. A, 66, 023805 (2002) [2] B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. Gühr, Science 322, 1232 (2008)
Origin of the energy level alignment at organic/organic interfaces: The role of structural defects

NASA Astrophysics Data System (ADS)

Bussolotti, Fabio; Yang, Jinpeng; Hinderhofer, Alexander; Huang, Yuli; Chen, Wei; Kera, Satoshi; Wee, Andrew T. S.; Ueno, Nobuo

2014-03-01

In this paper, the electronic properties of as-deposited and N2-exposedCuPc/F16CuPc interface, a prototype system for organic photovoltaic applications, are investigated by using ultralow background, high-sensitivity photoemission spectroscopy. It is found that (i) N2 exposure significantly modifies the energy level alignment (ELA) at the interface between CuPc and F16CuPc layer and (ii) the direction of the N2-induced energy level shift of the CuPc depends on the position of the Fermi level (EF) in the CuPc highest occupied molecular orbital-lowest unoccupied molecular orbital gap of the as-deposited film. These observations are related to the changes in the density of gap states (DOGS) produced by structural imperfections in the molecular packing geometry, as introduced by the N2 penetration into the CuPc layer. This result demonstrates the key role of structure-induced DOGS in controlling the ELA at organic/organic interfaces.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Jason W., E-mail: jwbarnes@uidaho.ed

Main-sequence stars earlier than spectral-type approxF6 or so are expected to rotate rapidly due to their radiative exteriors. This rapid rotation leads to an oblate stellar figure. It also induces the photosphere to be hotter (by up to several thousand kelvin) at the pole than at the equator as a result of a process called gravity darkening that was first predicted by von Zeipel. Transits of extrasolar planets across such a non-uniform, oblate disk yield unusual and distinctive lightcurves that can be used to determine the relative alignment of the stellar rotation pole and the planet orbit normal. This spin-orbitmore » alignment can be used to constrain models of planet formation and evolution. Orderly planet formation and migration within a disk that is coplanar with the stellar equator will result in spin-orbit alignment. More violent planet-planet scattering events should yield spin-orbit misaligned planets. Rossiter-McLaughlin measurements of transits of lower-mass stars show that some planets are spin-orbit aligned, and some are not. Since Rossiter-McLaughlin measurements are difficult around rapid rotators, lightcurve photometry may be the best way to determine the spin-orbit alignment of planets around massive stars. The Kepler mission will monitor approx10{sup 4} of these stars within its sample. The lightcurves of any detected planets will allow us to probe the planet formation process around high-mass stars for the first time.« less
Inflight alignment of payload inertial reference from Shuttle navigation system

NASA Astrophysics Data System (ADS)

Treder, A. J.; Norris, R. E.; Ruprecht, R.

Two methods for payload attitude initialization from the STS Orbiter have been proposed: body axis maneuvers (BAM) and star line maneuvers (SLM). The first achieves alignment directly through the Shuttle star tracker, while the second, indirectly through the stellar-updated Shuttle inertial platform. The Inertial Upper Stage (IUS) with its strapdown navigation system is used to demonstrate in-flight alignment techniques. Significant accuracy can be obtained with minimal impact on Orbiter operations, with payload inertial reference potentially approaching the accuracy of the Shuttle star tracker. STS-6 flight performance parameters, including alignment stability, are discussed and compared with operational complexity. Results indicate overall alignment stability of .06 deg, 3 sigma per axis.
Obtaining coincident image observations for Mission to Planet Earth science data return

NASA Technical Reports Server (NTRS)

Newman, Lauri Kraft; Folta, David C.; Farrell, James P.

1994-01-01

One objective of the Mission to Planet Earth (MTPE) program involves comparing data from various instruments on multiple spacecraft to obtain a total picture of the Earth's systems. To correlate image data from instruments on different spacecraft, these spacecraft must be able to image the same location on the Earth at approximately the same time. Depending on the orbits of the spacecraft involved, complicated operational details must be considered to obtain such observations. If the spacecraft are in similar orbits, close formation flying or synchronization techniques may be used to assure coincident observations. If the orbits are dissimilar, the launch time of the second satellite may need to be restricted in order to align its orbit with that of the first satellite launched. This paper examines strategies for obtaining coincident observations for spacecraft in both similar and dissimilar orbits. Although these calculations may be performed easily for coplanar spacecraft, the non-coplanar case involves additional considerations which are incorporated into the algorithms presented herein.
Theory and practice of uncommon molecular electronic configurations.

PubMed

Gryn'ova, Ganna; Coote, Michelle L; Corminboeuf, Clemence

2015-01-01

The electronic configuration of the molecule is the foundation of its structure and reactivity. The spin state is one of the key characteristics arising from the ordering of electrons within the molecule's set of orbitals. Organic molecules that have open-shell ground states and interesting physicochemical properties, particularly those influencing their spin alignment, are of immense interest within the up-and-coming field of molecular electronics. In this advanced review, we scrutinize various qualitative rules of orbital occupation and spin alignment, viz., the aufbau principle, Hund's multiplicity rule, and dynamic spin polarization concept, through the prism of quantum mechanics. While such rules hold in selected simple cases, in general the spin state of a system depends on a combination of electronic factors that include Coulomb and Pauli repulsion, nuclear attraction, kinetic energy, orbital relaxation, and static correlation. A number of fascinating chemical systems with spin states that fluctuate between triplet and open-shell singlet, and are responsive to irradiation, pH, and other external stimuli, are highlighted. In addition, we outline a range of organic molecules with intriguing non-aufbau orbital configurations. In such quasi-closed-shell systems, the singly occupied molecular orbital (SOMO) is energetically lower than one or more doubly occupied orbitals. As a result, the SOMO is not affected by electron attachment to or removal from the molecule, and the products of such redox processes are polyradicals. These peculiar species possess attractive conductive and magnetic properties, and a number of them that have already been developed into molecular electronics applications are highlighted in this review. WIREs Comput Mol Sci 2015, 5:440-459. doi: 10.1002/wcms.1233 For further resources related to this article, please visit the WIREs website.
The SOAPS project - Spin-orbit alignment of planetary systems. Exoplanets' evolution histories in systems with different architectures

NASA Astrophysics Data System (ADS)

Faedi, F.; Gómez Maqueo Chew, Y.; Fossati, L.; Pollacco, D.; McQuillan, A.; Hebb, L.; Chaplin, W. J.; Aigrain, S.

2013-04-01

The wealth of information rendered by Kepler planets and planet candidates is indispensable for statistically significant studies of distinct planet populations, in both single and multiple systems. Empirical evidences suggest that Kepler's planet population shows different physical properties as compared to the bulk of known exoplanets. The SOAPS project, aims to shed light on Kepler's planets formation, their migration and architecture. By measuring v sini accurately for Kepler hosts with rotation periods measured from their high-precision light curves, we will assess the alignment of the planetary orbit with respect to the stellar spin axis. This degree of alignment traces the formation history and evolution of the planetary systems, and thus, allows to distinguish between different proposed migration theories. SOAPS will increase by a factor of 2 the number of spin-orbit alignment measurements pushing the parameters space down to the SuperEarth domain. Here we present our preliminary results.

A Survey of Exoplanetary Spin-Orbit Angles

NASA Astrophysics Data System (ADS)

Winn, Josh

2010-02-01

Are the orbits of exoplanets aligned with the spin axes of their parent stars? One might expect a close alignment, but some of the proposed migration mechanisms predict otherwise. Indeed at least 4 planets with strongly tilted orbits are now known, including the first case of a retrograde or polar orbit. This raises the questions of how commonly misalignments occur, and which types of planets have them. We request 10 half-nights with Keck/HIRES spread over 2010A and 2010B, to measure spin-orbit angles for 9 exoplanets spanning a range of masses, periods, and eccentricities. Our measurement is based on the Rossiter-McLaughlin effect: the anomalous Doppler shift observed during planetary transits.
A Survey of Exoplanetary Spin-Orbit Angles

NASA Astrophysics Data System (ADS)

Winn, Josh

2010-08-01

Are the orbits of exoplanets aligned with the spin axes of their parent stars? One might expect a close alignment, but some of the proposed migration mechanisms predict otherwise. Indeed at least 4 planets with strongly tilted orbits are now known, including the first case of a retrograde or polar orbit. This raises the questions of how commonly misalignments occur, and which types of planets have them. We request 4 half-nights with Keck/HIRES spread over the 2010B semester, to measure spin-orbit angles for 4 exoplanets spanning a range of masses, periods, and eccentricities. Our measurement is based on the Rossiter-McLaughlin effect: the anomalous Doppler shift observed during planetary transits.
Comparison of two on-orbit attitude sensor alignment methods

NASA Technical Reports Server (NTRS)

Krack, Kenneth; Lambertson, Michael; Markley, F. Landis

1990-01-01

Compared here are two methods of on-orbit alignment of vector attitude sensors. The first method uses the angular difference between simultaneous measurements from two or more sensors. These angles are compared to the angular differences between the respective reference positions of the sensed objects. The alignments of the sensors are adjusted to minimize the difference between the two sets of angles. In the second method, the sensor alignment is part of a state vector that includes the attitude. The alignments are adjusted along with the attitude to minimize all observation residuals. It is shown that the latter method can result in much less alignment uncertainty when gyroscopes are used for attitude propagation during the alignment estimation. The additional information for this increased accuracy comes from knowledge of relative attitude obtained from the spacecraft gyroscopes. The theoretical calculations of this difference in accuracy are presented. Also presented are numerical estimates of the alignment uncertainties of the fixed-head star trackers on the Extreme Ultraviolet Explorer spacecraft using both methods.
ARE TIDAL EFFECTS RESPONSIBLE FOR EXOPLANETARY SPIN–ORBIT ALIGNMENT?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Gongjie; Winn, Joshua N., E-mail: gli@cfa.harvard.edu

The obliquities of planet-hosting stars are clues about the formation of planetary systems. Previous observations led to the hypothesis that for close-in giant planets, spin–orbit alignment is enforced by tidal interactions. Here, we examine two problems with this hypothesis. First, Mazeh and coworkers recently used a new technique—based on the amplitude of starspot-induced photometric variability—to conclude that spin–orbit alignment is common even for relatively long-period planets, which would not be expected if tides were responsible. We re-examine the data and find a statistically significant correlation between photometric variability and planetary orbital period that is qualitatively consistent with tidal interactions. Howevermore » it is still difficult to explain quantitatively, as it would require tides to be effective for periods as long as tens of days. Second, Rogers and Lin argued against a particular theory for tidal re-alignment by showing that initially retrograde systems would fail to be re-aligned, in contradiction with the observed prevalence of prograde systems. We investigate a simple model that overcomes this problem by taking into account the dissipation of inertial waves and the equilibrium tide, as well as magnetic braking. We identify a region of parameter space where re-alignment can be achieved, but it only works for close-in giant planets, and requires some fine tuning. Thus, while we find both problems to be more nuanced than they first appeared, the tidal model still has serious shortcomings.« less
Orbital alignment of circumbinary planets that form in misaligned circumbinary discs: the case of Kepler-413b

NASA Astrophysics Data System (ADS)

Pierens, A.; Nelson, R. P.

2018-06-01

Although most of the circumbinary planets detected by the Kepler spacecraft are on orbits that are closely aligned with the binary orbital plane, the systems Kepler-413 and Kepler-453 exhibit small misalignments of ˜2.5°. One possibility is that these planets formed in a circumbinary disc whose midplane was inclined relative to the binary orbital plane. Such a configuration is expected to lead to a warped and twisted disc, and our aim is to examine the inclination evolution of planets embedded in these discs. We employed 3D hydrodynamical simulations that examine the disc response to the presence of a modestly inclined binary with parameters that match the Kepler-413 system, as a function of disc parameters and binary inclinations. The discs all develop slowly varying warps, and generally display very small amounts of twist. Very slow solid body precession occurs because a large outer disc radius is adopted. Simulations of planets embedded in these discs resulted in the planet aligning with the binary orbit plane for disc masses close to the minimum mass solar nebular, such that nodal precession of the planet was controlled by the binary. For higher disc masses, the planet maintains near coplanarity with the local disc midplane. Our results suggest that circumbinary planets born in tilted circumbinary discs should align with the binary orbit plane as the disc ages and loses mass, even if the circumbinary disc remains misaligned from the binary orbit. This result has important implications for understanding the origins of the known circumbinary planets.
How do external companions affect spin-orbit misalignment of hot Jupiters?

NASA Astrophysics Data System (ADS)

Lai, Dong; Anderson, Kassandra R.; Pu, Bonan

2018-04-01

Consider a planet with its orbital angular momentum axis aligned with the spin axis of its host star. To what extent does an inclined distant companion (giant planet or binary star) affect this alignment? We provide an analytic, quantitative answer and apply it to hot Jupiter systems, for which misalignments between the orbital axis and the stellar spin axis have been detected. We also show how similar consideration can be applied to multiplanet systems with distant companions (such as Kepler-56). The result of this paper provides a simple method to assess the dynamical role played by external companions on spin-orbit misalignments in exoplanetary systems.
Elliptic Capture Orbits for Missions to the Near Planets

NASA Technical Reports Server (NTRS)

Casal, Federico G.; Swenson, Byron L.; Mascy, Alfred C.

1968-01-01

Elliptic capture orbits around Mars and Venus have often been considered as means for reducing arrival and departure energy requirements for two-way missions. It had also generally been feared that the energy savings obtained by capturing a spacecraft into a highly elliptical orbit (rather than a near circular orbit of the same periapsis) would largely be offset by the penalties incurred in aligning the semi-major axis of the ellipse in such a way as to obtain the proper orientation of the departure hyperbola. This paper, presents the results of an analysis which takes into consideration the penalties arising from the requirement to match the orientation of the elliptical orbit with the asymptote of the departure hyperbola. The scientific aspects of elliptical orbits around the target planet are discussed, and it is shown that such orbits exhibit characteristics which may be considered advantageous or disadvantageous depending on the purpose of the mission. Alignment of ' the semi-major axis of the capture, ellipse relative to the, asymptote of the escape hyperbola was found not to be a critical requirement since the kinetic energy remains high over a substantial portion of the elliptical capture orbit. This 'means that the escape stage can operate efficiently even when ignited at some angle from the true periapsis point. Considerable freedom in choosing this angle is available at little propulsive cost. The resulting latitude in the choice of angles between arrival and escape asymptotes makes it possible to consider a wide variety of interplanetary transfers and planetary staytimes without the need for separate propulsive maneuvers to realign the capture ellipse before departure., Special consideration has also been g1ven to plane change maneuvers around the planet. These may be required for reasons of orbit dynamics or scientific experimentation and are not uniquely tied to elliptical captures. The sensitivity of the mass of the excursion module to the eccentricity of the capture orbit is discussed and mass-penalty diagrams are presented. It is shown that these penalties do not materially offset the large gains obtained through the use of the elliptical capture mode.
Raman scattering studies of the orbital, magnetic, and conducting phases in double layer ruthenates

NASA Astrophysics Data System (ADS)

Karpus, John Francis

In this dissertation, light scattering techniques are used to probe the exotic orbital, magnetic, and conducting phases of the double layer ruthenate, Ca3Ru2O7, as functions of temperature, applied pressure, and applied magnetic field. These phases result from a rich interplay between the orbital, spin, and electronic degrees of freedom in such a strongly coupled system as Ca3Ru2O7. The Raman-active phonon and magnon excitations in Ca3Ru2O7 convey sufficient information to map out the orbital, magnetic, and conducting (H, T) and (P, T) phase diagrams of this material. This study finds that quasihydrostatic pressure causes a linear suppression of the orbital-ordering temperature (TOO = 48 K at P = 0), up to a T = 0 critical point near P* ˜ 55 kbar, above which the material is in a metallic, orbital-degenerate phase. This pressure-induced collapse of the antiferromagnetic orbital-ordered phase is associated with a suppression of the RuO6 octahedral distortions that are responsible for orbital-ordering. It is also shown that an applied magnetic field at low temperatures induces a change from an orbital-ordered to an orbital-degenerate phase for fields aligned along the in-plane hard-axis, but induces a reentrant orbital-ordered to orbital-disordered to orbital-ordered phase change for fields aligned along the in-plane easy-axis. This complex magnetic field dependence betrays the importance of the spin-orbit coupling in this system, which makes the field-induced phase behavior highly sensitive to both the applied magnetic field magnitude and direction. It is further shown that rapid field-induced changes in the structure and orbital populations are responsible for the highly field-tunable conducting properties of Ca3Ru2O7, and that the most dramatic magneto-conductivities are associated with an "orbital disordered" phase regime in which there is a random mixture of a- and b-axis oriented Ru moments and d-orbital populations on the Ru ions. Dilute La doping in Ca3Ru2O7 changes the lattice parameter along the c-axis and also adds an extra electron, providing bandwidth and band filling control, respectively. This addition of La also lowers the orbital ordering temperature to T ˜ 43 K, and provides a greater sensitivity of the orbital phases to applied magnetic fields, as evidenced by changes in the phases occurring at lower fields and over a greater field range than seen in the undoped system.
Speckle Interferometry of Red Dwarf Stars

NASA Astrophysics Data System (ADS)

Mason, Brian D.; Hartkopf, William I.; Miles, Korie N.; Subasavage, John P.; Raghavan, Deepak; Henry, Todd J.

2018-05-01

We report high-resolution optical speckle observations of 336 M dwarfs, which results in 113 measurements of the relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the systems. We also present the earliest measurements of relative position for 17 others. We include orbits for six of the systems, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.156 ± 0.011 and 0.1175+/- 0.0079 {{ \\mathcal M }}ȯ for the A and B components, respectively. All six of these new calculated orbits have short periods (between five and 38 years) and hold the promise of deriving accurate masses in the near future. For many other pairs we can establish their nature as physical or chance alignment, depending on their relative motion. Of the 80 systems, 32 have calculated orbits, 25 others are physical pairs, four are optical pairs, and 19 are currently unknown.
Linear analysis of the evolution of nearly polar low-mass circumbinary discs

NASA Astrophysics Data System (ADS)

Lubow, Stephen H.; Martin, Rebecca G.

2018-01-01

In a recent paper Martin & Lubow showed through simulations that an initially tilted disc around an eccentric binary can evolve to polar alignment in which the disc lies perpendicular to the binary orbital plane. We apply linear theory to show both analytically and numerically that a nearly polar aligned low-mass circumbinary disc evolves to polar alignment and determine the alignment time-scale. Significant disc evolution towards the polar state around moderately eccentric binaries can occur for typical protostellar disc parameters in less than a typical disc lifetime for binaries with orbital periods of order 100 yr or less. Resonant torques are much less effective at truncating the inner parts of circumbinary polar discs than the inner parts of coplanar discs. For polar discs, they vanish for a binary eccentricity of unity. The results agree with the simulations in showing that discs can evolve to a polar state. Circumbinary planets may then form in such discs and reside on polar orbits.
Analysis of Preferred Directions in Phase Space for Tidal Measurements at Europa

NASA Astrophysics Data System (ADS)

Boone, D.; Scheeres, D. J.

2012-12-01

The NASA Jupiter Europa Orbiter mission requires a circular, near-polar orbit to measure Europa's Love numbers, geophysical coefficients which give insight into whether a liquid ocean exists. This type of orbit about planetary satellites is known to be unstable. The effects of Jupiter's tidal gravity are seen in changes in Europa's gravity field and surface deformation, which are sensed through doppler tracking over time and altimetry measurements respectively. These two measurement types separately determine the h and k Love numbers, a combination of which bounds how thick the ice shell of Europa is and whether liquid water is present. This work shows how the properties of an unstable periodic orbit about Europa generate preferred measurement directions in position and velocity phase space for the orbit determination process. We generate an error covariance over seven days for the orbiter state and science parameters using a periodic orbit and then disperse the orbit initial conditions in a Monte Carlo simulation according to this covariance. The dispersed orbits are shown to have a bias toward longer lifetimes and we discuss this as an effect of the stable and unstable manifolds of the periodic orbit. Using an epoch formulation of a square-root information filter, measurements aligned with the unstable manifold mapped back in time add more information to the orbit determination process than measurements aligned with the stable manifold. This corresponds to a contraction in the uncertainty of the estimate of the desired parameters, including the Love numbers. We demonstrate this mapping mathematically using a representation of the State Transition Matrix involving its eigenvectors and eigenvalues. Then using the properties of left and right eigenvectors, we show how measurements in the orbit determination process are mapped in time leading to a concentration of information at epoch. We present examples of measurements taken on different time schedules to show the effect of preferred phase space directions in the estimation process. Manifold coordinate decomposition is applied to the orbit initial conditions as well as measurement partials in the filter to show the alignment of each with the stable and unstable manifolds of the periodic orbit. The connection between orbit lifetime and regions of increased information density in phase space is made using the properties of these manifolds. Low altitude, near-polar periodic orbits with these characteristics are discussed along with the estimation results for the Love numbers, orbiter state, and orbit lifetime. Different measurement schedules and the resulting estimation performance are presented along with an analysis of information content for single measurements with respect to manifold alignment. These results allow more sensitive estimation of the tidal Love numbers and may allow measurements to be taken less frequently or compensate for corrupted data arcs. Other measurement types will be mapped in the same way using the State Transition matrix and have increased information density at epoch if aligned with the unstable manifold. In the same way, these results are applicable to planetary satellite orbiters about Enceladus or Dione since they share the governing equations of motion and properties of unstable periodic orbits.
Gravitational wave searches for aligned-spin binary neutron stars using nonspinning templates

NASA Astrophysics Data System (ADS)

Cho, Hee-Suk; Lee, Chang-Hwan

2018-01-01

We study gravitational wave searches for merging binary neutron stars (NSs). We use nonspinning template waveforms towards the signals emitted from aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the orbital angular momentum. We use the TaylorF2 waveform model, which can generate inspiral waveforms emitted from aligned-spin compact binaries. We employ the single effective spin parameter χeff to represent the effect of two component spins (χ1, χ2) on the wave function. For a target system, we choose a binary consisting of the same component masses of 1.4 M ⊙ and consider the spins up to χ i = 0.4. We investigate fitting factors of the nonspinning templates to evaluate their efficiency in gravitational wave searches for the aligned-spin NS-NS binaries. We find that the templates can achieve the fitting factors exceeding 0.97 only for the signals in the range of -0.2 ≲ χeff ≲ 0. Therefore, we demonstrate the necessity of using aligned-spin templates not to lose the signals outside that range. We also show how much the recovered total mass can be biased from the true value depending on the spin of the signal.
High spin states of 72-74Kr

NASA Astrophysics Data System (ADS)

Kaushik, M.; Kumawat, M.; Singh, U. K.; Saxena, G.

2018-05-01

A theoretical investigation has made on the structure of high spin states of 72-74Kr within the framework of cranked Hartree-Fock-Bogoliubov (CHFB) theory employing a pairing + quadrupole + hexadecapole model interaction. Dependence of shape with the spin, excitation energy, alignment of proton as well as neutron 0g9/2 orbital along with backbending phenomenon are discussed upto a high spin J = 26. We found reasonable agreement with the experimental values and other theoretical calculations.
Landsat 8 thermal infrared sensor geometric characterization and calibration

USGS Publications Warehouse

Storey, James C.; Choate, Michael J.; Moe, Donald

2014-01-01

The Landsat 8 spacecraft was launched on 11 February 2013 carrying two imaging payloads: the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). The TIRS instrument employs a refractive telescope design that is opaque to visible wavelengths making prelaunch geometric characterization challenging. TIRS geometric calibration thus relied heavily on on-orbit measurements. Since the two Landsat 8 payloads are complementary and generate combined Level 1 data products, the TIRS geometric performance requirements emphasize the co-alignment of the OLI and TIRS instrument fields of view and the registration of the OLI reflective bands to the TIRS long-wave infrared emissive bands. The TIRS on-orbit calibration procedures include measuring the TIRS-to-OLI alignment, refining the alignment of the three TIRS sensor chips, and ensuring the alignment of the two TIRS spectral bands. The two key TIRS performance metrics are the OLI reflective to TIRS emissive band registration accuracy, and the registration accuracy between the TIRS thermal bands. The on-orbit calibration campaign conducted during the commissioning period provided an accurate TIRS geometric model that enabled TIRS Level 1 data to meet all geometric accuracy requirements. Seasonal variations in TIRS-to-OLI alignment have led to several small calibration parameter adjustments since commissioning.
Flight results of attitude matching between Space Shuttle and Inertial Upper Stage (IUS) navigation systems

NASA Astrophysics Data System (ADS)

Treder, Alfred J.; Meldahl, Keith L.

The recorded histories of Shuttle/Orbiter attitude and Inertial Upper Stage (IUS) attitude have been analyzed for all joint flights of the IUS in the Orbiter. This database was studied to determine the behavior of relative alignment between the IUS and Shuttle navigation systems. It is found that the overall accuracy of physical alignment has a Shuttle Orbiter bias component less than 5 arcmin/axis and a short-term stability upper bound of 0.5 arcmin/axis, both at 1 sigma. Summaries of the experienced physical and inertial alginment offsets are shown in this paper, together with alignment variation data, illustrated with some flight histories. Also included is a table of candidate values for some error source groups in an Orbiter/IUS attitude errror model. Experience indicates that the Shuttle is much more accurate and stable as an orbiting launch platform than has so far been advertised. This information will be valuable for future Shuttle payloads, especially those (such as the Aeroassisted Flight Experiment) which carry their own inertial navigation systems, and which could update or initialize their attitude determination systems using the Shuttle as the reference.
Improving magnetosphere in situ observations using solar sails

NASA Astrophysics Data System (ADS)

Parsay, Khashayar; Schaub, Hanspeter; Schiff, Conrad; Williams, Trevor

2018-01-01

Past and current magnetosphere missions employ conventional spacecraft formations for in situ observations of the geomagnetic tail. Conventional spacecraft flying in inertially fixed Keplerian orbits are only aligned with the geomagnetic tail once per year, since the geomagnetic tail is always aligned with the Earth-Sun line, and therefore, rotates annually. Solar sails are able to artificially create sun-synchronous orbits such that the orbit apse line remains aligned with the geomagnetic tail line throughout the entire year. This continuous presence in the geomagnetic tail can significantly increase the science phase for magnetosphere missions. In this paper, the problem of solar sail formation design is explored using nonlinear programming to design optimal two-craft, triangle, and tetrahedron solar sail formations, in terms of formation quality and formation stability. The designed formations are directly compared to the formations used in NASA's Magnetospheric Multi-Scale mission.
Auroral field-aligned current observations during the Cassini F-ring and Proximal orbits

NASA Astrophysics Data System (ADS)

Hunt, G. J.; Bunce, E. J.; Cao, H.; Cowley, S.; Dougherty, M. K.; Khurana, K. K.; Provan, G.; Southwood, D. J.

2017-12-01

Cassini's F-ring and Proximal orbits have provided a fantastic opportunity to examine Saturn's magnetic field closer to the planet than ever before. It is critical to understand external contributions to the azimuthal field component, as it can provide information on any asymmetry of the internal field. However, signatures of the auroral field-aligned currents are also present in this field component. Here we will identify and discuss these current signatures in the dawn and dusk sections in the northern and southern hemispheres, respectively. Previous results from observations during 2008 showed that in southern hemisphere these currents were strongly modulated by the southern planetary period oscillation (PPO) system. While the northern hemisphere data was modulated by both northern and southern PPOs, thus giving the first direct evidence of inter-hemispheric PPO currents. In both hemispheres, the PPO currents that give rise to the 10.7 h magnetic field oscillations observed throughout Saturn's magnetosphere, were separated from the PPO-independent (e.g. subcorotation) currents. These results provide a framework to which the Grand Finale orbits can be examined within. Here, we will assess how the field-aligned currents have evolved in comparison to the 2008 dataset. We will show that for the most part the observed field-aligned currents agree with the theoretical expectations. However, we will discuss the differences in terms of the PPO modulation, seasonal, and local time changes between the two datasets. Finally, we will discuss the implications of the azimuthal magnetic field contributions of these field-aligned currents on the data from the Proximal orbits.
Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

PubMed

Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

2016-04-22

We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.
The spatial extent of star formation in interacting galaxies

NASA Astrophysics Data System (ADS)

Moreno, Jorge

2015-08-01

We employ a suite of 75 simulations of galaxies in idealized major mergers (stellar mass ratio ˜2.5:1), with a wide range of orbital parameters, to investigate the spatial extent of interaction-induced star formation. Although the total star formation in galaxy encounters is generally elevated relative to isolated galaxies, we find that this elevation is a combination of intense enhancements within the central kpc and moderately suppressed activity at larger galactocentric radii. The radial dependence of the star formation enhancement is stronger in the less massive galaxy than in the primary, and is also more pronounced in mergers of more closely aligned disc spin orientations. Conversely, these trends are almost entirely independent of the encounter’s impact parameter and orbital eccentricity. Our predictions of the radial dependence of triggered star formation, and specifically the suppression of star formation beyond kpc-scales, will be testable with the next generation of integral-field spectroscopic surveys.Co-authors: Paul Torrey, Sara Ellison, David Patton, Asa Bluck, Gunjan Bansal & Lars Hernquist
Probing interfacial characteristics of rubrene/pentacene and pentacene/rubrene bilayers with soft X-ray spectroscopy.

PubMed

Seo, J H; Pedersen, T M; Chang, G S; Moewes, A; Yoo, K-H; Cho, S J; Whang, C N

2007-08-16

The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.

Orbital dynamics in the post-Newtonian planar circular restricted Sun-Jupiter system

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Dubeibe, F. L.

The theory of the post-Newtonian (PN) planar circular restricted three-body problem is used for numerically investigating the orbital dynamics of a test particle (e.g. a comet, asteroid, meteor or spacecraft) in the planar Sun-Jupiter system with a scattering region around Jupiter. For determining the orbital properties of the test particle, we classify large sets of initial conditions of orbits for several values of the Jacobi constant in all possible Hill region configurations. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping and (iii) collisional. Using the smaller alignment index (SALI) chaos indicator, we further classify bounded orbits into regular, sticky or chaotic. In order to get a spherical view of the dynamics of the system, the grids of the initial conditions of the orbits are defined on different types of two-dimensional planes. We locate the different types of basins and we also relate them with the corresponding spatial distributions of the escape and collision time. Our thorough analysis exposes the high complexity of the orbital dynamics and exhibits an appreciable difference between the final states of the orbits in the classical and PN approaches. Furthermore, our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant, along with a remarkable presence of fractal basin boundaries. Our outcomes are compared with the earlier ones regarding other planetary systems.
Kepler's Second Law and Synodic Period.

ERIC Educational Resources Information Center

Mariner, James L.; Horner, Jack K.

1981-01-01

Discusses kinematics of the planetary alignment in nature and related results. Describes a model of planetary alignments to beginning astronomy students. The model is to explain Jupiter's deviation from a circular orbit. (SK)
THE INFLUENCE OF MAGNETIC FIELD GEOMETRY ON THE FORMATION OF CLOSE-IN EXOPLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, Jacob B., E-mail: jbsimon.astro@gmail.com

2016-08-20

Approximately half of Sun-like stars harbor exoplanets packed within a radius of ∼0.3 au, but the formation of these planets and why they form in only half of known systems are still not well understood. We employ a one-dimensional steady-state model to gain physical insight into the origin of these close-in exoplanets. We use Shakura and Sunyaev α values extracted from recent numerical simulations of protoplanetary disk accretion processes in which the magnitude of α , and thus the steady-state gas surface density, depend on the orientation of large-scale magnetic fields with respect to the disk’s rotation axis. Solving formore » the metallicity as a function of radius, we find that for fields anti-aligned with the rotation axis, the inner regions of our model disk often fall within a region of parameter space that is not suitable for planetesimal formation, whereas in the aligned case, the inner disk regions are likely to produce planetesimals through some combination of streaming instability and gravitational collapse, though the degree to which this is true depends on the assumed parameters of our model. More robustly, the aligned field case always produces higher concentrations of solids at small radii compared to the anti-aligned case. In the in situ formation model, this bimodal distribution of solid enhancement leads directly to the observed dichotomy in exoplanet orbital distances.« less
A trajectory generation and system characterization model for cislunar low-thrust spacecraft. Volume 2: Technical manual

NASA Technical Reports Server (NTRS)

Korsmeyer, David J.; Pinon, Elfego, III; Oconnor, Brendan M.; Bilby, Curt R.

1990-01-01

The documentation of the Trajectory Generation and System Characterization Model for the Cislunar Low-Thrust Spacecraft is presented in Technical and User's Manuals. The system characteristics and trajectories of low thrust nuclear electric propulsion spacecraft can be generated through the use of multiple system technology models coupled with a high fidelity trajectory generation routine. The Earth to Moon trajectories utilize near Earth orbital plane alignment, midcourse control dependent upon the spacecraft's Jacobian constant, and capture to target orbit utilizing velocity matching algorithms. The trajectory generation is performed in a perturbed two-body equinoctial formulation and the restricted three-body formulation. A single control is determined by the user for the interactive midcourse portion of the trajectory. The full spacecraft system characteristics and trajectory are provided as output.
High-harmonic spectroscopy of aligned molecules

NASA Astrophysics Data System (ADS)

Yun, Hyeok; Yun, Sang Jae; Lee, Gae Hwang; Nam, Chang Hee

2017-01-01

High harmonics emitted from aligned molecules driven by intense femtosecond laser pulses provide the opportunity to explore the structural information of molecules. The field-free molecular alignment technique is an expedient tool for investigating the structural characteristics of linear molecules. The underlying physics of field-free alignment, showing the characteristic revival structure specific to molecular species, is clearly explained from the quantum-phase analysis of molecular rotational states. The anisotropic nature of molecules is shown from the harmonic polarization measurement performed with spatial interferometry. The multi-orbital characteristics of molecules are investigated using high-harmonic spectroscopy, applied to molecules of N2 and CO2. In the latter case the two-dimensional high-harmonic spectroscopy, implemented using a two-color laser field, is applied to distinguish harmonics from different orbitals. Molecular high-harmonic spectroscopy will open a new route to investigate ultrafast dynamics of molecules.
Optical Modeling Activities for NASA's James Webb Space Telescope (JWST): V. Operational Alignment Updates

NASA Technical Reports Server (NTRS)

Howard, Joseph M.; Ha, Kong Q.; Shiri, Ron; Smith, J. Scott; Mosier, Gary; Muheim, Danniella

2008-01-01

This paper is part five of a series on the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two papers discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third paper investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory, and the fourth introduced the software toolkits used to perform much of the optical analysis for JWST. The work here models observatory operations by simulating line-of-sight image motion and alignment drifts over a two-week period. Alignment updates are then simulated using wavefront sensing and control processes to calculate and perform the corrections. A single model environment in Matlab is used for evaluating the predicted performance of the observatory during these operations.
Investigation of the charge-orbital ordering mechanism in single-layered Pr0.5Ca1.5MnO4

NASA Astrophysics Data System (ADS)

Rangkuti, C. N.; Majidi, M. A.

2018-04-01

Motivated by the experimental study of half-doped single-layered Pr0.5Ca1.5MnO4 showing charge, orbital, and spin orderings [1], we propose a model to theoretically study the system to explain such ordering phenomena. The ground state electron configuration reveals that the charges form a checkerboard pattern with alternating Mn3+/Mn4+ sites, while the orbitals are aligned in zigzag chains [1, 2]. We calculate the ground state energy of this system to find the most preferable configuration by comparing three types of configurations (charge-unordered, charge-ordered, and charge-orbital-ordered states). The calculations are based on a tight-binding model representing effective electron hoppings among Mn ions in MnO2-plane. We take into account the horizontally- and vertically-oriented orbital and spin degrees of freedom at Mn sites. We assume that the hopping integral values depend on the relative orientation between the corresponding orbitals of adjacent Mn ions. The interaction terms we incorporate into our effective Hamiltonian include inter-orbital, intra-orbital Hubbard repulsions, and Jahn-Teller distortion [2]. We absorb the exchange interaction between spins into local self-energy that we calculate within dynamical mean field algorithm [2]. Within our model we show a circumstance in which the charge-orbital ordered configuration has the lowest energy, consistent with the ground state ordering revealed by the experimental data.
THE GRAVITATIONAL INTERACTION BETWEEN PLANETS ON INCLINED ORBITS AND PROTOPLANETARY DISKS AS THE ORIGIN OF PRIMORDIAL SPIN–ORBIT MISALIGNMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsakos, Titos; Königl, Arieh

Many of the observed spin–orbit alignment properties of exoplanets can be explained in the context of the primordial disk misalignment model, in which an initially aligned protoplanetary disk is torqued by a distant stellar companion on a misaligned orbit, resulting in a precessional motion that can lead to large-amplitude oscillations of the spin–orbit angle. We consider a variant of this model in which the companion is a giant planet with an orbital radius of a few astronomical units. Guided by the results of published numerical simulations, we model the dynamical evolution of this system by dividing the disk into inner andmore » outer parts—separated at the location of the planet—that behave as distinct, rigid disks. We show that the planet misaligns the inner disk even as the orientation of the outer disk remains unchanged. In addition to the oscillations induced by the precessional motion, whose amplitude is larger the smaller the initial inner-disk-to-planet mass ratio, the spin–orbit angle also exhibits a secular growth in this case—driven by ongoing mass depletion from the disk—that becomes significant when the inner disk’s angular momentum drops below that of the planet. Altogether, these two effects can produce significant misalignment angles for the inner disk, including retrograde configurations. We discuss these results within the framework of the Stranded Hot Jupiter scenario and consider their implications, including the interpretation of the alignment properties of debris disks.« less
47 CFR 25.209 - Antenna performance standards.

Code of Federal Regulations, 2011 CFR

2011-10-01

... below the envelope defined below: (1) In the plane of the geostationary satellite orbit as it appears at... geostationary satellite orbit as it appears at the particular earth station location, for earth stations... aligned with the plane of the geostationary satellite orbit as it appears at the particular earth station...
47 CFR 25.209 - Antenna performance standards.

Code of Federal Regulations, 2010 CFR

2010-10-01

... below the envelope defined below: (1) In the plane of the geostationary satellite orbit as it appears at... geostationary satellite orbit as it appears at the particular earth station location, for earth stations... aligned with the plane of the geostationary satellite orbit as it appears at the particular earth station...
47 CFR 25.209 - Antenna performance standards.

Code of Federal Regulations, 2012 CFR

2012-10-01

... below the envelope defined below: (1) In the plane of the geostationary satellite orbit as it appears at... geostationary satellite orbit as it appears at the particular earth station location, for earth stations... aligned with the plane of the geostationary satellite orbit as it appears at the particular earth station...
MAGNETOHYDRODYNAMIC SIMULATION OF A DISK SUBJECTED TO LENSE-THIRRING PRECESSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sorathia, Kareem A.; Krolik, Julian H.; Hawley, John F.

2013-11-01

When matter orbits around a central mass obliquely with respect to the mass's spin axis, the Lense-Thirring effect causes it to precess at a rate declining sharply with radius. Ever since the work of Bardeen and Petterson, it has been expected that when a fluid fills an orbiting disk, the orbital angular momentum at small radii should then align with the mass's spin. Nearly all previous work has studied this alignment under the assumption that a phenomenological 'viscosity' isotropically degrades fluid shears in accretion disks, even though it is now understood that internal stress in flat disks is due tomore » anisotropic MHD turbulence. In this paper we report a pair of matched simulations, one in MHD and one in pure (non-viscous) HD in order to clarify the specific mechanisms of alignment. As in the previous work, we find that disk warps induce radial flows that mix angular momentum of different orientation; however, we also show that the speeds of these flows are generically transonic and are only very weakly influenced by internal stresses other than pressure. In particular, MHD turbulence does not act in a manner consistent with an isotropic viscosity. When MHD effects are present, the disk aligns, first at small radii and then at large; alignment is only partial in the HD case. We identify the specific angular momentum transport mechanisms causing alignment and show how MHD effects permit them to operate more efficiently. Last, we relate the speed at which an alignment front propagates outward (in the MHD case) to the rate at which Lense-Thirring torques deliver angular momentum at smaller radii.« less
A Ninth Planet in Our Solar System?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-01-01

The recent discovery that the orbits of some Kuiper belt objects (KBOs) share properties has proved puzzling. A pair of scientists have now proposed a bold explanation: there may be a planet-sized object yet undetected in our solar system.Mysterious ClusteringKBOs, the population of mainly small objects beyond Neptune, have proven an especially interesting subject of study in the last decade as many small, distant bodies (such as Eris, the object that led to the demotion of Pluto to dwarf planet) have been discovered.Previous studies have recently discovered that some especially distant KBOs those that orbit with semimajor axes of a 150 AU, nearly four times that of Pluto all cross the ecliptic at a similar phase in their elliptical trajectories. This is unexpected, since gravitational tugs from the giant planets should have randomized this parameter over our solar systems multi-billion-year lifespan.Physical alignment of the orbits of Kuiper belt objects with a 250 AU (and two objects with a 150 AU that are dynamically stable). [Batygin Brown 2016]Two scientists at California Institute of Technology, Konstantin Batygin and Michael Brown (you might recognize Brown as the man who killed Pluto) have now increased the mystery. In a recently published a study, they demonstrate that for KBOs that have orbits with a 250 AU, the orbits are actually physically aligned.To explain this unexpected alignment which Batygin and Brown calculate has only a 0.007% probability of having occurred by chance the authors ask an exciting question: could this be caused by the presence of an unseen, large, perturbing body further out in the solar system?Simulating a Ninth PlanetThe authors test this hypothesis by carrying out both analytical calculations and numerical N-body simulations designed to determine if the gravitational influence of a distant, planetary-mass companion can explain the behavior we observe from the large-orbit KBOs.Simulation of the effect of a distant planet (M = 10 M, a = 700 AU, and e = 0.6) on KBOs; click for a better look! The perihelion position of KBOs with a 250 AU clusters around 180 from the perihelion position of the perturbing planet. More-transparent points are less observable. [Batygin Brown 2016]The result? It turns out that such a distant planet can cause the orbits of KBOs with a 250 AU to all align in the opposite direction of the orbit of the planet. Whats more, the gravitational pull of this planet can also explain other unresolved puzzles about the Kuiper belt, such as the presence of high-perihelion Sedna-like objects, as well as a population of KBOs weve observed that have misaligned orbits.Unfortunately, Batygin and Brown found it isnt possible to exactly determine the properties of the possible planet, since multiple combinations of its mass, eccentricity, and semimajor axis can create the same observational results. That said, they believe the distant perturbers orbit is highly eccentric, its orbital inclination is low, and its fairly massive (since anything less than an Earth-mass wont create the observed clustering of KBO orbits within the age of the solar system).As an example, one possible set of parameters that approximately reproduces the observed KBO orbits is the following:planet mass of 10 Earth-massessemi-major axis of a = 700 AUeccentricity of e = 0.6This would correspond to a perihelion distance of 280 AU and an aphelion distance of 1,120 AU.The authors speculate such a planet might have been formed closer in to the Sun, but it was ejected later on during our solar systems evolution. Interactions with the Suns birth cluster could have then caused the planet to be retained in a bound orbit.Future TestsOur solar system on a logarithmic scale (click for the full view). KBOs with a semimajor axis of a 250 AU may be being aligned by a planetary-mass body with an even more distant orbit. [NASA]How can we test this hypothesis of a ninth planet? Obviously, directly observing the planet would confirm its presence. But the authors model has an additional testable hypothesis: if its correct, there should be a population of high-perihelion Kuiper belt objects that dont exhibit the same alignment of their orbits as the KBOs we know about, but instead have opposite-aligned orbits. If we discover such a collection of objects, that would be an excellent confirmation of this model.The authors caution that their work is preliminary, and additional investigation will be required to better understand the possibilities presented here. But with any luck, future theoretical work, as well as observational tests of this models predictions, will help us determine whether there might be a distant ninth planet in our solar system!BonusCheck out this video (created with WWT!), which walks us first through a view of the six aligned KBO orbits, then shows a possible orbit for the hypothesized planet, and then shows an additional population of already-discovered objects (also predicted by the model) that have orbits perpendicular both to the plane of the solar system and to the planets orbit. [Caltech/Robert Hurt]http://aasnova.org/wp-content/uploads/2016/01/Planet9_anim_720.m4vCitationKonstantin Batygin and Michael E. Brown 2016 AJ 151 22. doi:10.3847/0004-6256/151/2/22
Charge Transfer and Orbital Level Alignment at Inorganic/Organic Interfaces: The Role of Dielectric Interlayers.

PubMed

Hollerer, Michael; Lüftner, Daniel; Hurdax, Philipp; Ules, Thomas; Soubatch, Serguei; Tautz, Frank Stefan; Koller, Georg; Puschnig, Peter; Sterrer, Martin; Ramsey, Michael G

2017-06-27

It is becoming accepted that ultrathin dielectric layers on metals are not merely passive decoupling layers, but can actively influence orbital energy level alignment and charge transfer at interfaces. As such, they can be important in applications ranging from catalysis to organic electronics. However, the details at the molecular level are still under debate. In this study, we present a comprehensive analysis of the phenomenon of charge transfer promoted by a dielectric interlayer with a comparative study of pentacene adsorbed on Ag(001) with and without an ultrathin MgO interlayer. Using scanning tunneling microscopy and photoemission tomography supported by density functional theory, we are able to identify the orbitals involved and quantify the degree of charge transfer in both cases. Fractional charge transfer occurs for pentacene adsorbed on Ag(001), while the presence of the ultrathin MgO interlayer promotes integer charge transfer with the lowest unoccupied molecular orbital transforming into a singly occupied and singly unoccupied state separated by a large gap around the Fermi energy. Our experimental approach allows a direct access to the individual factors governing the energy level alignment and charge-transfer processes for molecular adsorbates on inorganic substrates.
Planet formation in binary systems: simulating coagulation using analytically determined collision velocities.

NASA Astrophysics Data System (ADS)

Silsbee, Kedron; Rafikov, Roman

2017-06-01

The existence of planets in tight binary systems presents an interesting puzzle. It is thought that cores of giant planets form via agglomeration of planetesimals in mutual collisions. However, in tight binary systems, one would naïvely expect the collision velocities between planetesimals to be so high that even 100 km bodies would be destroyed, rather than growing in mutual collisions. In these systems, planetesimals are perturbed by gravity from the companion star, and gravity and gas drag from a massive eccentric gas disk. There is a damaging secular resonance that occurs due to the combination of disk gravity and gravity from the binary companion, however the disk gravity can also create locations of low relative eccentricity between planetesimals of different sizes that would not exist if the disk gravity were ignored. Because the gas drag acts more strongly on smaller planetesimals, orbital eccentricity and apsidal angle depend on planetesimal size. Consequently, planetesimal collision velocities depend on the sizes of the collision partners. Same-size bodies collide at low velocity because their orbits are apsidally aligned. Therefore, often in a given environment some collisions will lead to planetesimal growth, and some to erosion or destruction. This variety of collisional outcomes makes it difficult to determine whether any planetesimals can grow to large sizes. We run a multi-annulus coagulation/fragmentation simulation that also includes the effect of size-dependent radial drift of planetesimals to determine the minimum size of initial planetesimal necessary for growth to large sizes in collisions. The minimum initial size of planetesimal necessary for growth depends greatly on the disk mass, eccentricity and the degree of apsidal alignment with the binary. We find that in a wide variety of situations, it is a reasonable approximation that growth occurs as long as there are no collisions capable of completely destroying a planetesimal, but erosion by moderately damaging collisions can also prevent growth from occurring.
Saturn's Magnetic Field from the Cassini Grand Finale orbits

NASA Astrophysics Data System (ADS)

Dougherty, M. K.; Cao, H.; Khurana, K. K.; Hunt, G. J.; Provan, G.; Kellock, S.; Burton, M. E.; Burk, T. A.

2017-12-01

The fundamental aims of the Cassini magnetometer investigation during the Cassini Grand Finale orbits were determination of Saturn's internal planetary magnetic field and the rotation rate of the deep interior. The unique geometry of the orbits provided an unprecedented opportunity to measure the intrinsic magnetic field at close distances never before encountered. The surprising close alignment of Saturn's magnetic axis with its spin axis, known about since the days of Pioneer 11, has been a focus of the team's analysis since Cassini Saturn Orbit Insertion. However, the varying northern and southern magnetospheric planetary period oscillations, which fill the magnetosphere, has been a factor in masking the field signals from the interior. Here we describe an overview of the magnetometer results from the Grand Finale orbits, including confirmation of the extreme axisymmetric nature of the planetary magnetic field, implications for knowledge of the rotation rate and the behaviour of external magnetic fields (arising from the ring current, field aligned currents both at high and low latitudes and the modulating effect of the planetary period oscillations).
A PRIMER ON UNIFYING DEBRIS DISK MORPHOLOGIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu, E-mail: echiang@astro.berkeley.edu

A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, diskmore » inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.« less
Forecasting Tidal Disruption Events for Binary Black Holes with an Outer Tertiary.

PubMed

Seto, Naoki; Kyutoku, Koutarou

2017-04-14

We discuss the gravitational wave (GW) emission and the orbital evolution of a hierarchical triple system composed of an inner binary black hole (BBH) and an outer tertiary. Depending on the kick velocity at the merger, the merged BBH could tidally disrupt the tertiary. Even though the fraction of BBH mergers accompanied by such disruptions is expected to be much smaller than unity, the existence of a tertiary and its basic parameters (e.g., semimajor axis, projected mass) can be examined for more than 10^{3} BBHs with the follow-on missions to the space GW detector LISA. This allows us to efficiently prescreen the targets for the follow-up searches for the tidal disruption events (TDEs). The TDE probability would be significantly higher for triple systems with aligned orbital- and spin-angular momenta, compared with random configurations.
3D Printing of Molecular Models with Calculated Geometries and p Orbital Isosurfaces

ERIC Educational Resources Information Center

Carroll, Felix A.; Blauch, David N.

2017-01-01

3D printing was used to prepare models of the calculated geometries of unsaturated organic structures. Incorporation of p orbital isosurfaces into the models enables students in introductory organic chemistry courses to have hands-on experience with the concept of orbital alignment in strained and unstrained p systems.
Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star

NASA Astrophysics Data System (ADS)

Bourrier, Vincent; Lovis, Christophe; Beust, Hervé; Ehrenreich, David; Henry, Gregory W.; Astudillo-Defru, Nicola; Allart, Romain; Bonfils, Xavier; Ségransan, Damien; Delfosse, Xavier; Cegla, Heather M.; Wyttenbach, Aurélien; Heng, Kevin; Lavie, Baptiste; Pepe, Francesco

2018-01-01

The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin–orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Addison, B. C.; Tinney, C. G.; Wright, D. J.

We have measured the sky-projected spin–orbit alignments for three transiting hot Jupiters, WASP-103b, WASP-87b, and WASP-66b, using spectroscopic measurements of the Rossiter–McLaughlin effect, with the CYCLOPS2 optical fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky-projected spin–orbit angles of λ = 3° ± 33°, λ = −8° ± 11°, and λ = −4° ± 22° for WASP-103b, WASP-87b, and WASP-66b, respectively, suggest that these three planets are likely on nearly aligned orbits with respect to their host star’s spin axis. WASP-103 is a particularly interesting system as its orbital distance is only 20% larger thanmore » its host star’s Roche radius and the planet likely experiences strong tidal effects. WASP-87 and WASP-66 are hot ( T {sub eff} = 6450 ± 120 K and T {sub eff} = 6600 ± 150 K, respectively) mid-F stars, making them similar to the majority of stars hosting planets on high-obliquity orbits. Moderate spin–orbit misalignments for WASP-103b and WASP-66b are consistent with our data, but polar and retrograde orbits are not favored for these systems.« less
Innermost stable circular orbit of spinning particle in charged spinning black hole background

NASA Astrophysics Data System (ADS)

Zhang, Yu-Peng; Wei, Shao-Wen; Guo, Wen-Di; Sui, Tao-Tao; Liu, Yu-Xiao

2018-04-01

In this paper we investigate the innermost stable circular orbit (ISCO) (spin-aligned or anti-aligned orbit) for a classical spinning test particle with the pole-dipole approximation in the background of Kerr-Newman black hole in the equatorial plane. It is shown that the orbit of the spinning particle is related to the spin of the test particle. The motion of the spinning test particle will be superluminal if its spin is too large. We give an additional condition by considering the superluminal constraint for the ISCO in the black hole backgrounds. We obtain numerically the relations between the ISCO and the properties of the black holes and the test particle. It is found that the radius of the ISCO for a spinning test particle is smaller than that of a nonspinning test particle in the black hole backgrounds.
Control of exciton confinement in quantum dot-organic complexes through energetic alignment of interfacial orbitals.

PubMed

Frederick, Matthew T; Amin, Victor A; Swenson, Nathaniel K; Ho, Andrew Y; Weiss, Emily A

2013-01-09

This paper describes a method to control the quantum confinement, and therefore the energy, of excitonic holes in CdSe QDs through adsorption of the hole-delocalizing ligand phenyldithiocarbamate, PTC, and para substitutions of the phenyl ring of this ligand with electron-donating or -withdrawing groups. These substitutions control hole delocalization in the QDs through the energetic alignment of the highest occupied orbitals of PTC with the highest density-of-states region of the CdSe valence band, to which PTC couples selectively.
Hubble Space Telescope high speed photometer orbital verification

NASA Technical Reports Server (NTRS)

Richards, Evan E.

1991-01-01

The purpose of this report is to provide a summary of the results of the HSP (High Speed Photometer) Orbital Verification (OV) tests and to report conclusions and lessons learned from the initial operations of the HSP. The HSP OV plan covered the activities through fine (phase 3) alignment. This report covers all activities (OV, SV, and SAO) from launch to the completion of phase 3 alignment. Those activities in this period that are not OV tests are described to the extent that they relate to OV activities.
THE FINAL SPIN FROM BINARY BLACK HOLES IN QUASI-CIRCULAR ORBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hofmann, Fabian; Rezzolla, Luciano; Barausse, Enrico

2016-07-10

We revisit the problem of predicting the spin magnitude and direction of the black hole (BH) resulting from the merger of two BHs with arbitrary masses and spins inspiraling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit, and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formulamore » is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding an rms error σ ≈ 0.002 for aligned/anti-aligned binaries and σ ≈ 0.006 for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors.« less
Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Dubeibe, Fredy L.; González, Guillermo A.

2018-07-01

The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modelled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping, and (iii) displaying close encounters. Using the smaller alignment index chaos indicator, we further classify bounded orbits into regular, sticky, or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.
Influence of seasonal cycles in Martian atmosphere on entry, descent and landing sequence

NASA Astrophysics Data System (ADS)

Marčeta, Dušan; Šegan, Stevo; Rašuo, Boško

2014-05-01

The phenomena like high eccentricity of Martian orbit, obliquity of the orbital plane and close alignment of the winter solstice and the orbital perihelion, separately or together can significantly alter not only the level of some Martian atmospheric parameters but also the characteristics of its diurnal and seasonal cycle. Considering that entry, descent and landing (EDL) sequence is mainly driven by the density profile of the atmosphere and aerodynamic characteristic of the entry vehicle. We have performed the analysis of the influence of the seasonal cycles of the atmospheric parameters on EDL profiles by using Mars Global Reference Atmospheric Model (Mars-GRAM). Since the height of the deployment of the parachute and the time passed from the deployment to propulsion firing (descent time) are of crucial importance for safe landing and the achievable landing site elevation we paid special attention to the influence of the areocentric longitude of the Sun (Ls) on these variables. We have found that these variables have periodic variability with respect to Ls and can be very well approximated with a sine wave function whose mean value depends only on the landing site elevation while the amplitudes and phases depend only on the landing site latitude. The amplitudes exhibit behavior which is symmetric with respect to the latitude but the symmetry is shifted from the equator to the northern mid-tropics. We have also noticed that the strong temperature inversions which are usual for middle and higher northern latitudes while Mars is around its orbital perihelion significantly alter the descent time without influencing the height of the parachute deployment. At last, we applied our model to determine the dependence of the accessible landing region on Ls and found that this region reaches maximum when Mars is around the orbital perihelion and can vary 50° in latitude throughout the Martian year.
THE BANANA PROJECT. III. SPIN-ORBIT ALIGNMENT IN THE LONG-PERIOD ECLIPSING BINARY NY CEPHEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albrecht, Simon; Winn, Joshua N.; Carter, Joshua A.

Binaries are not always neatly aligned. Previous observations of the DI Her system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here, we report on a measurement of the spin-axis orientation of the primary star of the NY Cep system, which is similar to DI Her in many respects: it features two young early-type stars ({approx}6 Myr, B0.5V+B2V), in an eccentric and relatively long-period orbit (e = 0.48, P = 15fd3). The sky projections of the rotation vector and the spin vector are well aligned ({beta}{sub p} =more » 2{sup 0} {+-} 4{sup 0}), in strong contrast to DI Her. Although no convincing explanation has yet been given for the misalignment of DI Her, our results show that the phenomenon is not universal, and that a successful theory will need to account for the different outcome in the case of NY Cep.« less
Space Technology 5 Multi-point Measurements of Near-Earth Magnetic Fields: Initial Results

NASA Technical Reports Server (NTRS)

Slavin, James A.; Le, G.; Strangeway, R. L.; Wang, Y.; Boardsen, S.A.; Moldwin, M. B.; Spence, H. E.

2007-01-01

The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 x 4500 km dawn-dusk orbit on 22 March 2006. Each spacecraft carried a boom-mounted vector fluxgate magnetometer that returned highly sensitive and accurate measurements of the geomagnetic field. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of approximately 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness and current density. In doing so, we demonstrate two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit; 1) the "standard method," based upon s/c velocity, but corrected for FAC current sheet motion, and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data set and expand to include geomagnetic field gradient analyses as well as field-aligned and ionospheric currents.
Internal alignment and position resolution of the silicon tracker of DAMPE determined with orbit data

NASA Astrophysics Data System (ADS)

Tykhonov, A.; Ambrosi, G.; Asfandiyarov, R.; Azzarello, P.; Bernardini, P.; Bertucci, B.; Bolognini, A.; Cadoux, F.; D'Amone, A.; De Benedittis, A.; De Mitri, I.; Di Santo, M.; Dong, Y. F.; Duranti, M.; D'Urso, D.; Fan, R. R.; Fusco, P.; Gallo, V.; Gao, M.; Gargano, F.; Garrappa, S.; Gong, K.; Ionica, M.; La Marra, D.; Lei, S. J.; Li, X.; Loparco, F.; Marsella, G.; Mazziotta, M. N.; Peng, W. X.; Qiao, R.; Salinas, M. M.; Surdo, A.; Vagelli, V.; Vitillo, S.; Wang, H. Y.; Wang, J. Z.; Wang, Z. M.; Wu, D.; Wu, X.; Zhang, F.; Zhang, J. Y.; Zhao, H.; Zimmer, S.

2018-06-01

The DArk Matter Particle Explorer (DAMPE) is a space-borne particle detector designed to probe electrons and gamma-rays in the few GeV to 10 TeV energy range, as well as cosmic-ray proton and nuclei components between 10 GeV and 100 TeV. The silicon-tungsten tracker-converter is a crucial component of DAMPE. It allows the direction of incoming photons converting into electron-positron pairs to be estimated, and the trajectory and charge (Z) of cosmic-ray particles to be identified. It consists of 768 silicon micro-strip sensors assembled in 6 double layers with a total active area of 6.6 m2. Silicon planes are interleaved with three layers of tungsten plates, resulting in about one radiation length of material in the tracker. Internal alignment parameters of the tracker have been determined on orbit, with non-showering protons and helium nuclei. We describe the alignment procedure and present the position resolution and alignment stability measurements.
Cornering characteristics of the main-gear tire of the space shuttle orbiter

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.; Robinson, Martha P.

1988-01-01

An experimental investigation was conducted at the NASA Langley Research Center to study the effects of various vertical load and yaw angle conditions on the cornering behavior of the Space Shuttle Orbiter main gear tire. Measured parameters included side and drag force, side and drag force coefficients, aligning torque, and overturning torque. Side force coefficient was found to increase as yaw angle was increased, but decreased as the vertical load was increased. Drag force was found to increase as vertical load was increased at constant yaw angles. Aligning torque measurements indicated that the tire is stable in yaw.
Non-linear tides in a homogeneous rotating planet or star: global modes and elliptical instability

NASA Astrophysics Data System (ADS)

Barker, Adrian J.; Braviner, Harry J.; Ogilvie, Gordon I.

2016-06-01

We revisit the global modes and instabilities of homogeneous rotating ellipsoidal fluid masses, which are the simplest global models of rotationally and tidally deformed gaseous planets or stars. The tidal flow in a short-period planet may be unstable to the elliptical instability, a hydrodynamic instability that can drive tidal evolution. We perform a global (and local WKB) analysis to study this instability using the elegant formalism of Lebovitz & Lifschitz. We survey the parameter space of global instabilities with harmonic orders ℓ ≤ 5, for planets with spins that are purely aligned (prograde) or anti-aligned (retrograde) with their orbits. In general, the instability has a much larger growth rate if the planetary spin and orbit are anti-aligned rather than aligned. We have identified a violent instability for anti-aligned spins outside of the usual frequency range for the elliptical instability (when n/Ω ≲ -1, where n and Ω are the orbital and spin angular frequencies, respectively) if the tidal amplitude is sufficiently large. We also explore the instability in a rigid ellipsoidal container, which is found to be quantitatively similar to that with a realistic free surface. Finally, we study the effect of rotation and tidal deformation on mode frequencies. We find that larger rotation rates and larger tidal deformations both decrease the frequencies of the prograde sectoral surface gravity modes. This increases the prospect of their tidal excitation, potentially enhancing the tidal response over expectations from linear theory. In a companion paper, we use our results to interpret global simulations of the elliptical instability.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Nutzman, Philip A.; Fabrycky, Daniel C.; Fortney, Jonathan J., E-mail: pnutzman@ucolick.org

Spectroscopic follow-up of dozens of transiting planets has revealed the degree of alignment between the equators of stars and the orbits of the planets they host. Here we determine a method, applicable to spotted stars, that can reveal the same information from the photometric discovery data, with no need for follow-up. A spot model fit to the global light curve, parameterized by the spin orientation of the star, predicts when the planet will transit the spots. Observing several spot crossings during different transits then leads to constraints on the spin-orbit alignment. In cases where stellar spots are small, the stellarmore » inclination, i{sub s} , and hence the true alignment, rather than just the sky projection, can be obtained. This method has become possible with the advent of space telescopes such as CoRoT and Kepler, which photometrically monitor transiting planets over a nearly continuous, long time baseline. We apply our method to CoRoT-2 and find the projected spin-orbit alignment angle, {lambda} = 4.{sup 0}7 {+-} 12.{sup 0}3, in excellent agreement with a previous determination that employed the Rossiter-McLaughlin effect. The large spots of the parent star, CoRoT-2, limit our precision on i{sub s} : 84{sup 0} {+-} 36{sup 0}, where i{sub s} < 90{sup 0}(> 90{sup 0}) indicates that the rotation axis is tilted toward (away from) the line of sight.« less
Precessional Instability in Binary Black Holes with Aligned Spins.

PubMed

Gerosa, Davide; Kesden, Michael; O'Shaughnessy, Richard; Klein, Antoine; Berti, Emanuele; Sperhake, Ulrich; Trifirò, Daniele

2015-10-02

Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values r(ud±)=(√(χ(1))±√(qχ(2)))(4)(1-q)(-2)M, where M is the total mass, q≡m(2)/m(1) is the mass ratio, and χ(1) (χ(2)) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.
On-orbit checkout of satellites, volume 2. Part 3 of on-orbit checkout study. [space maintenance

NASA Technical Reports Server (NTRS)

Pritchard, E. I.

1978-01-01

Early satellite failures significantly degrading satellite operations are reviewed with emphasis on LANDSAT D, the Technology Demonstration Satellite, the ATREX/AEM spacecraft, STORMSAT 2, and the synchronous meteorological satellite. Candidates for correction with on-orbit checkout and appropriate actions are analyzed. On-orbit checkout subsystem level studies are summarized for electrical power, attitude control, thermal control, reaction control and propulsion, instruments, and angular rate matching for alignment of satellite IRU.
Energy level alignment at planar organic heterojunctions: influence of contact doping and molecular orientation.

PubMed

Opitz, Andreas

2017-04-05

Planar organic heterojunctions are widely used in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. The energy level alignment in the devices plays an important role in obtaining the aspired gap arrangement. Additionally, the π-orbital overlap between the involved molecules defines e.g. the charge-separation efficiency in solar cells due to charge-transfer effects. To account for both aspects, direct/inverse photoemission spectroscopy and near edge x-ray absorption fine structure spectroscopy were used to determine the energy level landscape and the molecular orientation at prototypical planar organic heterojunctions. The combined experimental approach results in a comprehensive model for the electronic and morphological characteristics of the interface between the two investigated molecular semiconductors. Following an introduction on heterojunctions used in devices and on energy levels of organic materials, the energy level alignment of planar organic heterojunctions will be discussed. The observed energy landscape is always determined by the individual arrangement between the energy levels of the molecules and the work function of the electrode. This might result in contact doping due to Fermi level pinning at the electrode for donor/acceptor heterojunctions, which also improves the solar cell efficiency. This pinning behaviour can be observed across an unpinned interlayer and results in charge accumulation at the donor/acceptor interface, depending on the transport levels of the respective organic semiconductors. Moreover, molecular orientation will affect the energy levels because of the anisotropy in ionisation energy and electron affinity and is influenced by the structural compatibility of the involved molecules at the heterojunction. High structural compatibility leads to π-orbital stacking between different molecules at a heterojunction, which is of additional interest for photovoltaic active interfaces and for ground-state charge-transfer.
Orbital Alignment of Main-belt Comets

NASA Astrophysics Data System (ADS)

Kim, Yoonyoung; JeongAhn, Youngmin; Hsieh, Henry H.

2018-03-01

We examine the orbital element distribution of main-belt comets (MBCs), which are objects that exhibit cometary activity yet orbit in the main asteroid belt and may be potentially useful as tracers of ice in the inner solar system. We find that the currently known and currently active MBCs have remarkably similar longitudes of perihelion, which are also aligned with that of Jupiter. The clustered objects have significantly higher current osculating eccentricities relative to their proper eccentricities, consistent with their orbits being currently, though only temporarily, secularly excited in osculating eccentricity due to Jupiter’s influence. At the moment, most MBCs seem to have current osculating elements that may be particularly favorable for the object becoming active (e.g., maybe because of higher perihelion temperatures or higher impact velocities causing an effective increase in the size of the potential triggering impactor population). At other times, other icy asteroids will have those favorable conditions and might become MBCs at those times as well.
Final implementation, commissioning, and performance of embedded collimator beam position monitors in the Large Hadron Collider

NASA Astrophysics Data System (ADS)

Valentino, Gianluca; Baud, Guillaume; Bruce, Roderik; Gasior, Marek; Mereghetti, Alessio; Mirarchi, Daniele; Olexa, Jakub; Redaelli, Stefano; Salvachua, Belen; Valloni, Alessandra; Wenninger, Jorg

2017-08-01

During Long Shutdown 1, 18 Large Hadron Collider (LHC) collimators were replaced with a new design, in which beam position monitor (BPM) pick-up buttons are embedded in the collimator jaws. The BPMs provide a direct measurement of the beam orbit at the collimators, and therefore can be used to align the collimators more quickly than using the standard technique which relies on feedback from beam losses. Online orbit measurements also allow for reducing operational margins in the collimation hierarchy placed specifically to cater for unknown orbit drifts, therefore decreasing the β* and increasing the luminosity reach of the LHC. In this paper, the results from the commissioning of the embedded BPMs in the LHC are presented. The data acquisition and control software architectures are reviewed. A comparison with the standard alignment technique is provided, together with a fill-to-fill analysis of the measured orbit in different machine modes, which will also be used to determine suitable beam interlocks for a tighter collimation hierarchy.
High-order harmonic generation from highly excited states in acetylene

NASA Astrophysics Data System (ADS)

Mulholland, Peter; Dundas, Daniel

2018-04-01

High-order harmonic generation (HHG) from aligned acetylene molecules interacting with mid infra-red (IR), linearly polarized laser pulses is studied theoretically using a mixed quantum-classical approach in which the electrons are described using time-dependent density-functional theory while the ions are treated classically. We find that for molecules aligned perpendicular to the laser polarization axis, HHG arises from the highest-occupied molecular orbital (HOMO), while for molecules aligned along the laser polarization axis, HHG is dominated by the HOMO-1. In the parallel orientation we observe a double plateau with an inner plateau that is produced by ionization from and recombination back to an autoionizing state. Two pieces of evidence support this idea. First, by choosing a suitably tuned vacuum ultraviolet pump pulse that directly excites the autoionizing state we observe a dramatic enhancement of all harmonics in the inner plateau. Second, in certain circumstances, the position of the inner plateau cutoff does not agree with the classical three-step model. We show that this discrepancy can be understood in terms of a minimum in the dipole recombination matrix element from the continuum to the autoionizing state.
The spatial structure of magnetospheric plasma disturbance estimated by using magnetic data obtained by SWARM satellites.

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Iyemori, T.; Aoyama, T.

2017-12-01

Field-aligned currents with various spatial scales flow into and out from high-latitude ionosphere. The magnetic fluctuations observed by LEO satellites along their orbits having period longer than a few seconds can be regarded as the manifestations of spatial structure of field aligned currents.This has been confirmed by using the initial orbital characteristics of 3 SWARM-satellites. From spectral analysis, we evaluated the spectral indices of these magnetic fluctuations and investigated their dependence on regions, such as magnetic latitude and MLT and so on. We found that the spectral indices take quite different values between the regions lower than the equatorward boundary of the auroral oval (around 63 degrees' in magnetic latitude) and the regions higher than that. On the other hands, we could not find the clear MLT dependence. In general, the FACs are believed to be generated in the magnetiospheric plasma sheet and boundary layer, and they flow along the field lines conserving their currents.The theory of FAC generation [e.g., Hasegawa and Sato ,1978] indicates that the FACs are strongly connected with magnetospheric plasma disturbances. Although the spectral indices above are these of spatial structures of the FACs over the ionosphere, by using the theoretical equation of FAC generation, we evaluate the spectral indices of magnetospheric plasma disturbance in FAC's generation regions. Furthermore, by projecting the area of fluctuations on the equatorial plane of magnetosphere (i.e. plasma sheet), we can estimate the spatial structure of magnetospheric plasma disturbance. In this presentation, we focus on the characteristics of disturbance in midnight region and discuss the relations to the substorm.

Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Dubeibe, F. L.; González, Guillermo A.

2018-04-01

The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modeled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping and (iii) displaying close encounters. Using the smaller alignment index (SALI) chaos indicator, we further classify bounded orbits into regular, sticky or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Albrecht, Simon; Winn, Joshua N.; Marcy, Geoffrey W.

We measure the sky-projected stellar obliquities ({lambda}) in the multiple-transiting planetary systems KOI-94 and Kepler-25, using the Rossiter-McLaughlin effect. In both cases, the host stars are well aligned with the orbital planes of the planets. For KOI-94 we find {lambda} = -11 Degree-Sign {+-} 11 Degree-Sign , confirming a recent result by Hirano and coworkers. Kepler-25 was a more challenging case, because the transit depth is unusually small (0.13%). To obtain the obliquity, it was necessary to use prior knowledge of the star's projected rotation rate and apply two different analysis methods to independent wavelength regions of the spectra. Themore » two methods gave consistent results, {lambda} = 7 Degree-Sign {+-} 8 Degree-Sign and -0. Degree-Sign 5 {+-} 5. Degree-Sign 7. There are now a total of five obliquity measurements for host stars of systems of multiple-transiting planets, all of which are consistent with spin-orbit alignment. This alignment is unlikely to be the result of tidal interactions because of the relatively large orbital distances and low planetary masses in the systems. In this respect, the multiplanet host stars differ from hot-Jupiter host stars, which commonly have large spin-orbit misalignments whenever tidal interactions are weak. In particular, the weak-tide subset of hot-Jupiter hosts has obliquities consistent with an isotropic distribution (p = 0.6), but the multiplanet hosts are incompatible with such a distribution (p {approx} 10{sup -6}). This suggests that high obliquities are confined to hot-Jupiter systems, and provides further evidence that hot-Jupiter formation involves processes that tilt the planetary orbit.« less
Dynamical Analysis of the Circumprimary Planet in the Eccentric Binary System HD 59686

NASA Astrophysics Data System (ADS)

Trifonov, Trifon; Lee, Man Hoi; Reffert, Sabine; Quirrenbach, Andreas

2018-04-01

We present a detailed orbital and stability analysis of the HD 59686 binary-star planet system. HD 59686 is a single-lined, moderately close (a B = 13.6 au) eccentric (e B = 0.73) binary, where the primary is an evolved K giant with mass M = 1.9 M ⊙ and the secondary is a star with a minimum mass of m B = 0.53 M ⊙. Additionally, on the basis of precise radial velocity (RV) data, a Jovian planet with a minimum mass of m p = 7 M Jup, orbiting the primary on a nearly circular S-type orbit with e p = 0.05 and a p = 1.09 au, has recently been announced. We investigate large sets of orbital fits consistent with HD 59686's RV data by applying bootstrap and systematic grid search techniques coupled with self-consistent dynamical fitting. We perform long-term dynamical integrations of these fits to constrain the permitted orbital configurations. We find that if the binary and the planet in this system have prograde and aligned coplanar orbits, there are narrow regions of stable orbital solutions locked in a secular apsidal alignment with the angle between the periapses, Δω, librating about 0°. We also test a large number of mutually inclined dynamical models in an attempt to constrain the three-dimensional orbital architecture. We find that for nearly coplanar and retrograde orbits with mutual inclination 145° ≲ Δi ≤ 180°, the system is fully stable for a large range of orbital solutions.
Landsat 8 operational land imager on-orbit geometric calibration and performance

USGS Publications Warehouse

Storey, James C.; Choate, Michael J.; Lee, Kenton

2014-01-01

The Landsat 8 spacecraft was launched on 11 February 2013 carrying the Operational Land Imager (OLI) payload for moderate resolution imaging in the visible, near infrared (NIR), and short-wave infrared (SWIR) spectral bands. During the 90-day commissioning period following launch, several on-orbit geometric calibration activities were performed to refine the prelaunch calibration parameters. The results of these calibration activities were subsequently used to measure geometric performance characteristics in order to verify the OLI geometric requirements. Three types of geometric calibrations were performed including: (1) updating the OLI-to-spacecraft alignment knowledge; (2) refining the alignment of the sub-images from the multiple OLI sensor chips; and (3) refining the alignment of the OLI spectral bands. The aspects of geometric performance that were measured and verified included: (1) geolocation accuracy with terrain correction, but without ground control (L1Gt); (2) Level 1 product accuracy with terrain correction and ground control (L1T); (3) band-to-band registration accuracy; and (4) multi-temporal image-to-image registration accuracy. Using the results of the on-orbit calibration update, all aspects of geometric performance were shown to meet or exceed system requirements.
XUV ionization of aligned molecules

NASA Astrophysics Data System (ADS)

Kelkensberg, F.; Rouzée, A.; Siu, W.; Gademann, G.; Johnsson, P.; Lucchini, M.; Lucchese, R. R.; Vrakking, M. J. J.

2011-11-01

New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO2 molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, D. J. A.; Collier Cameron, A.; Enoch, B.

We present measurements of the spin-orbit alignment angle, {lambda}, for the hot Jupiter systems WASP-32, WASP-38, and HAT-P-27/WASP-40, based on data obtained using the HARPS spectrograph. We analyze the Rossiter-McLaughlin effect for all three systems and also carry out Doppler tomography for WASP-32 and WASP-38. We find that WASP-32 (T {sub eff} = 6140{sup +90} {sub -100} K) is aligned, with an alignment angle of {lambda} = 10.{sup 0}5{sup +6.4} {sub -6.5} obtained through tomography, and that WASP-38 (T {sub eff} = 6180{sup +40} {sub -60} K) is also aligned, with tomographic analysis yielding {lambda} = 7.{sup 0}5{sup +4.7} {submore » -6.1}. The latter result provides an order-of-magnitude improvement in the uncertainty in {lambda} compared to the previous analysis of Simpson et al. We are only able to loosely constrain the angle for HAT-P-27/WASP-40 (T{sub eff} = 5190{sup +160} {sub -170} K) to {lambda} = 24.{sup 0}2{sup +76.0}{sub -44.5}, owing to the poor signal-to-noise ratio of our data. We consider this result a non-detection under a slightly updated version of the alignment test of Brown et al. We place our results in the context of the full sample of spin-orbit alignment measurements, finding that they provide further support for previously established trends.« less
Effect of amino on spin-dependent transport through a junction of fused oligothiophenes between graphene electrodes

NASA Astrophysics Data System (ADS)

Cao, Liemao; Li, Xiaobo; Liu, Guang; Liu, Ziran; Zhou, Guanghui

2017-05-01

The influence of chemical side groups is significant in physical or chemical understanding the transport through the single molecular junction. Motivated by the recent successful fabrication and measurement of a single organic molecule sandwiched between graphene electrodes (Prins et al., 2011), here we study the spin-dependent transport properties through a junction of a fused oligothiophenes molecule embedded between two zigzag-edged graphene nanoribbon (ZGNR) electrodes. The molecule with and without an attached amino NH2 side group is considered, respectively, and external magnetic fields or FM stripes are applied onto the ZGNRs to initially orient the magnetic alignment of the electrodes for the spin-dependent consideration. By the ab initio calculations based on the density functional theory combined with nonequilibrium Green's function formalism, we have demonstrated the remarkable difference in the spin-charge transport property between the junctions of the molecule with and without NH2 side group. In particular, the junction with side group shows more obvious NDR. In addition, it exhibits an interesting dual spin-filtering effect when the magnetic alignment in electrodes is initially antiparallel-oriented. The mechanisms of the results are revealed and discussed in terms of the spin-resolved transmission spectrum associated with the frontier molecular orbitals evolution, the molecular projected self-consistent Hamiltonian eigenvalues, and the local density of states.
Maintaining Aura's Orbit Requirements While Performing Orbit Maintenance Maneuvers Containing an Orbit Normal Delta-V Component

NASA Technical Reports Server (NTRS)

Johnson, Megan R.; Petersen, Jeremy D.

2014-01-01

The Earth Observing System (EOS) Afternoon Constellation consists of five member missions (GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura), each of which maintain a frozen, sun-synchronous orbit with a 16-day repeating ground track that follows the Worldwide Reference System-2 (WRS-2). Under nominal science operations for Aura, the propulsion system is oriented such that the resultant thrust vector is aligned 13.493 degrees away from the velocity vector along the yaw axis. When performing orbit maintenance maneuvers, the spacecraft performs a yaw slew to align the thrust vector in the appropriate direction. A new Drag Make Up (DMU) maneuver operations scheme has been implemented for Aura alleviating the need for the 13.493 degree yaw slew. The focus of this investigation is to assess the impact that no-slew DMU maneuver operations will have on Aura's Mean Local Time (MLT) which drives the required along track separation between Aura and the constellation members, as well as Aura's frozen orbit properties, eccentricity and argument of perigee. Seven maneuver strategies were analyzed to determine the best operational approach. A mirror pole strategy, with maneuvers alternating at the North and South poles, was implemented operationally to minimize impact to the MLT. Additional analysis determined that the mirror pole strategy could be further modified to include frozen orbit maneuvers and thus maintain both MLT and the frozen orbit properties under noslew operations.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Winn, Joshua N.; Albrecht, Simon; Johnson, John Asher

We find the orbit of the Neptune-sized exoplanet HAT-P-11b to be highly inclined relative to the equatorial plane of its host star. This conclusion is based on spectroscopic observations of two transits, which allowed the Rossiter-McLaughlin effect to be detected with an amplitude of 1.5 m s{sup -1}. The sky-projected obliquity is 103{sup +26} {sub -10} deg. This is the smallest exoplanet for which spin-orbit alignment has been measured. The result favors a migration scenario involving few-body interactions followed by tidal dissipation. This finding also conforms with the pattern that the systems with the weakest tidal interactions have the widestmore » spread in obliquities. We predict that the high obliquity of HAT-P-11 will be manifest in transit light curves from the Kepler spacecraft: starspot-crossing anomalies will recur at most once per stellar rotation period, rather than once per orbital period as they would for a well-aligned system.« less
Exterior Companions to Hot Jupiters Orbiting Cool Stars Are Coplanar

NASA Astrophysics Data System (ADS)

Becker, Juliette C.; Vanderburg, Andrew; Adams, Fred C.; Khain, Tali; Bryan, Marta

2017-12-01

The existence of hot Jupiters has challenged theories of planetary formation since the first extrasolar planets were detected. Giant planets are generally believed to form far from their host stars, where volatile materials like water exist in their solid phase, making it easier for giant planet cores to accumulate. Several mechanisms have been proposed to explain how giant planets can migrate inward from their birth sites to short-period orbits. One such mechanism, called Kozai-Lidov migration, requires the presence of distant companions in orbits inclined by more than ˜40° with respect to the plane of the hot Jupiter’s orbit. The high occurrence rate of wide companions in hot-Jupiter systems lends support to this theory for migration. However, the exact orbital inclinations of these detected planetary and stellar companions is not known, so it is not clear whether the mutual inclination of these companions is large enough for the Kozai-Lidov process to operate. This paper shows that in systems orbiting cool stars with convective outer layers, the orbits of most wide planetary companions to hot Jupiters must be well aligned with the orbits of the hot Jupiters and the spins of the host stars. For a variety of possible distributions for the inclination of the companion, the width of the distribution must be less than ˜20° to recreate the observations with good fidelity. As a result, the companion orbits are likely well aligned with those of the hot Jupiters, and the Kozai-Lidov mechanism does not enforce migration in these systems.
XUV ionization of aligned molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelkensberg, F.; Siu, W.; Gademann, G.

2011-11-15

New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO{sub 2} molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.
The Oblique Orbit of WASP-107b from K2 Photometry

NASA Astrophysics Data System (ADS)

Dai, Fei; Winn, Joshua N.

2017-05-01

Observations of nine transits of WASP-107 during the K2 mission reveal three separate occasions when the planet crossed in front of a starspot. The data confirm the stellar rotation period to be 17 days—approximately three times the planet’s orbital period—and suggest that large spots persist for at least one full rotation. If the star had a low obliquity, at least two additional spot crossings should have been observed. They were not observed, giving evidence for a high obliquity. We use a simple geometric model to show that the obliquity is likely in the range 40°-140°, I.e., both spin-orbit alignment and anti-alignment can be ruled out. WASP-107 thereby joins the small collection of relatively low-mass stars with a high obliquity. Most such stars have been observed to have low obliquities; all of the exceptions, including WASP-107, involve planets with relatively wide orbits (“warm Jupiters,” with {a}{{\\min }}/{R}\\star ≳ 8). This demonstrates a connection between stellar obliquity and planet properties, in contradiction to some theories for obliquity excitation.
John F. Kennedy Space Center's Wireless Hang Angle Instrumentation System

NASA Technical Reports Server (NTRS)

Kohler, Jeff

2009-01-01

The technology is a high-precision, wireless inclinometer. The system was designed for monitoring the suspension angle of the Orbiter vehicle during loading onto the Solid Rocket Boosters of the Space Shuttle. Originally, operators manually measured the alignment of the Orbiter with a hand-held inclinometer on a nonrigid surface. The measurement was open to interpretation by the loader. If the Orbiter is misaligned, it can crush ball joints and delay the loading while repairs are made. With this system, the Orbiter can be loaded without damage and without manual measurement.
Methods and devices for measuring orbital angular momentum states of electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMorran, Benjamin J.; Harvey, Tyler R.

A device for measuring electron orbital angular momentum states in an electron microscope includes the following components aligned sequentially in the following order along an electron beam axis: a phase unwrapper (U) that is a first electrostatic refractive optical element comprising an electrode and a conductive plate, where the electrode is aligned perpendicular to the conductive plate; a first electron lens system (L1); a phase corrector (C) that is a second electrostatic refractive optical element comprising an array of electrodes with alternating electrostatic bias; and a second electron lens system (L2). The phase unwrapper may be a needle electrode ormore » knife edge electrode.« less
A general intermolecular force field based on tight-binding quantum chemical calculations

NASA Astrophysics Data System (ADS)

Grimme, Stefan; Bannwarth, Christoph; Caldeweyher, Eike; Pisarek, Jana; Hansen, Andreas

2017-10-01

A black-box type procedure is presented for the generation of a molecule-specific, intermolecular potential energy function. The method uses quantum chemical (QC) information from our recently published extended tight-binding semi-empirical scheme (GFN-xTB) and can treat non-covalently bound complexes and aggregates with almost arbitrary chemical structure. The necessary QC information consists of the equilibrium structure, Mulliken atomic charges, charge centers of localized molecular orbitals, and also of frontier orbitals and orbital energies. The molecular pair potential includes model density dependent Pauli repulsion, penetration, as well as point charge electrostatics, the newly developed D4 dispersion energy model, Drude oscillators for polarization, and a charge-transfer term. Only one element-specific and about 20 global empirical parameters are needed to cover systems with nuclear charges up to radon (Z = 86). The method is tested for standard small molecule interaction energy benchmark sets where it provides accurate intermolecular energies and equilibrium distances. Examples for structures with a few hundred atoms including charged systems demonstrate the versatility of the approach. The method is implemented in a stand-alone computer code which enables rigid-body, global minimum energy searches for molecular aggregation or alignment.
Supercurrent in ferromagnetic Josephson junctions with heavy metal interlayers

NASA Astrophysics Data System (ADS)

Satchell, Nathan; Birge, Norman O.

2018-06-01

The length scale over which supercurrent from conventional BCS, s -wave superconductors (S ) can penetrate an adjacent ferromagnetic (F ) layer depends on the ability to convert singlet Cooper pairs into triplet Cooper pairs. Spin-aligned triplet Cooper pairs are not dephased by the ferromagnetic exchange interaction and can thus penetrate an F layer over much longer distances than singlet Cooper pairs. These triplet Cooper pairs carry a dissipationless spin current and are the fundamental building block for the fledgling field of superspintronics. Singlet-triplet conversion by inhomogeneous magnetism is well established. Here, we describe an attempt to use spin-orbit coupling as an alternative mechanism to mediate singlet-triplet conversion in S-F-S Josephson junctions. We report that the addition of thin Pt spin-orbit-coupling layers in our Josephson junctions significantly increases supercurrent transmission, however the decay length of the supercurrent is not found to increase. We attribute the increased supercurrent transmission to Pt acting as a buffer layer to improve the growth of the Co F layer.
Observation of anisotropic interactions between metastable atoms and target molecules by two-dimensional collisional ionization electron spectroscopy

NASA Astrophysics Data System (ADS)

Kishimoto, Naoki; Ohno, Koichi

Excited metastable atoms colliding with target molecules can sensitively probe outer properties of molecules by chemi-ionization (Penning ionization) from molecular orbitals in the outer region, since metastable atoms cannot penetrate into the repulsive interaction wall around the molecules. By means of two-dimensional measurements using kinetic energy analysis of electrons combined with a velocity-resolved metastable beam, one can obtain information on the anisotropic interaction between the colliding particles without any control of orientation or alignment of target molecules. We have developed a classical trajectory method to calculate the collision energy dependence of partial ionization cross-sections (CEDPICS) on the anisotropic interaction potential energy surface, which has enabled us to study stereodynamics between metastable atoms and target molecules as well as the spatial distribution of molecular orbitals and electron ejection functions which have a relation with entrance and exit channels of the reaction. Based on the individual CEDPICS, the electronic structure of molecules can also be elucidated.
Spin-orbit coupling induced two-electron relaxation in silicon donor pairs

NASA Astrophysics Data System (ADS)

Song, Yang; Das Sarma, S.

2017-09-01

We unravel theoretically a key intrinsic relaxation mechanism among the low-lying singlet and triplet donor-pair states in silicon, an important element in the fast-developing field of spintronics and quantum computation. Despite the perceived weak spin-orbit coupling (SOC) in Si, we find that our discovered relaxation mechanism, combined with the electron-phonon and interdonor interactions, drives the transitions in the two-electron states over a large range of donor coupling regimes. The scaling of the relaxation rate with interdonor exchange interaction J goes from J5 to J4 at the low to high temperature limits. Our analytical study draws on the symmetry analysis over combined band, donor envelope, and valley configurations. It uncovers naturally the dependence on the donor-alignment direction and triplet spin orientation, and especially on the dominant SOC source from donor impurities. While a magnetic field is not necessary for this relaxation, unlike in the single-donor spin relaxation, we discuss the crossover behavior with increasing Zeeman energy in order to facilitate comparison with experiments.
Evolution of Binary Supermassive Black Holes in Rotating Nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasskazov, Alexander; Merritt, David

The interaction of a binary supermassive black hole with stars in a galactic nucleus can result in changes to all the elements of the binary’s orbit, including the angles that define its orientation. If the nucleus is rotating, the orientation changes can be large, causing large changes in the binary’s orbital eccentricity as well. We present a general treatment of this problem based on the Fokker–Planck equation for f , defined as the probability distribution for the binary’s orbital elements. First- and second-order diffusion coefficients are derived for the orbital elements of the binary using numerical scattering experiments, and analyticmore » approximations are presented for some of these coefficients. Solutions of the Fokker–Planck equation are then derived under various assumptions about the initial rotational state of the nucleus and the binary hardening rate. We find that the evolution of the orbital elements can become qualitatively different when we introduce nuclear rotation: (1) the orientation of the binary’s orbit evolves toward alignment with the plane of rotation of the nucleus and (2) binary orbital eccentricity decreases for aligned binaries and increases for counteraligned ones. We find that the diffusive (random-walk) component of a binary’s evolution is small in nuclei with non-negligible rotation, and we derive the time-evolution equations for the semimajor axis, eccentricity, and inclination in that approximation. The aforementioned effects could influence gravitational wave production as well as the relative orientation of host galaxies and radio jets.« less
Testing and Calibration of Phase Plates for JWST Optical Simulator

NASA Technical Reports Server (NTRS)

Gong, Qian; Chu, Jenny; Tournois, Severine; Eichhorn, William; Kubalak, David

2011-01-01

Three phase plates were designed to simulate the JWST segmented primary mirror wavefront at three on-orbit alignment stages: coarse phasing, intermediate phasing, and fine phasing. The purpose is to verify JWST's on-orbit wavefront sensing capability. Amongst the three stages, coarse alignment is defined to have piston error between adjacent segments being 30 m to 300 m, intermediate being 0.4 m to 10 m, and fine is below 0.4 m. The phase plates were made of fused silica, and were assembled in JWST Optical Simulator (OSIM). The piston difference was realized by the thickness difference of two adjacent segments. The two important parameters to phase plates are piston and wavefront errors. Dispersed Fringe Sensor (DFS) method was used for initial coarse piston evaluation, which is the emphasis of this paper. Point Diffraction Interferometer (PDI) is used for fine piston and wavefront error. In order to remove piston's 2 pi uncertainty with PDI, three laser wavelengths, 640nm, 660nm, and 780nm, are used for the measurement. The DHS test setup, analysis algorithm and results are presented. The phase plate design concept and its application (i.e. verifying the JWST on-orbit alignment algorithm) are described. The layout of JWST OSIM and the function of phase plates in OSIM are also addressed briefly.

In-flight angular alignment of inertial navigation systems by means of radio aids

NASA Technical Reports Server (NTRS)

Tanner, W.

1972-01-01

The principles involved in the angular alignment of the inertial reference by nondirectional data from radio aids are developed and compared with conventional methods of alignment such as gyro-compassing and pendulous vertical determination. The specific problem is considered of the space shuttle reentry and a proposed technique for the alignment of the inertial reference system some time before landing. A description is given of the digital simulation of a transponder interrogation system and of its interaction with the inertial navigation system. Data from reentry simulations are used to demonstrate the effectiveness of in-flight inertial system alignment. Concluding remarks refer to other potential applications such as space shuttle orbit insertion and air navigation of conventional aircraft.
Two Small Transiting Planets and a Possible Third Body Orbiting HD 106315

NASA Astrophysics Data System (ADS)

Crossfield, Ian J. M.; Ciardi, David R.; Isaacson, Howard; Howard, Andrew W.; Petigura, Erik A.; Weiss, Lauren M.; Fulton, Benjamin J.; Sinukoff, Evan; Schlieder, Joshua E.; Mawet, Dimitri; Ruane, Garreth; de Pater, Imke; de Kleer, Katherine; Davies, Ashley G.; Christiansen, Jessie L.; Dressing, Courtney D.; Hirsch, Lea; Benneke, Björn; Crepp, Justin R.; Kosiarek, Molly; Livingston, John; Gonzales, Erica; Beichman, Charles A.; Knutson, Heather A.

2017-06-01

The masses, atmospheric makeups, spin-orbit alignments, and system architectures of extrasolar planets can be best studied when the planets orbit bright stars. We report the discovery of three bodies orbiting HD 106315, a bright (V = 8.97 mag) F5 dwarf targeted by our K2 survey for transiting exoplanets. Two small transiting planets are found to have radii {2.23}-0.25+0.30 {R}\\oplus and {3.95}-0.39+0.42 {R}\\oplus and orbital periods 9.55 days and 21.06 days, respectively. A radial velocity (RV) trend of 0.3 ± 0.1 m s-1 day-1 indicates the likely presence of a third body orbiting HD 106315 with period ≳160 days and mass ≳45 M ⊕. Transits of this object would have depths ≳0.1% and are definitively ruled out. Although the star has v sin I = 13.2 km s-1, it exhibits a short-timescale RV variability of just 6.4 m s-1. Thus, it is a good target for RV measurements of the mass and density of the inner two planets and the outer object’s orbit and mass. Furthermore, the combination of RV noise and moderate v sin I makes HD 106315 a valuable laboratory for studying the spin-orbit alignment of small planets through the Rossiter-McLaughlin effect. Space-based atmospheric characterization of the two transiting planets via transit and eclipse spectroscopy should also be feasible. This discovery demonstrates again the power of K2 to find compelling exoplanets worthy of future study.
Southwest Research Institute astronomer Dan Durda checks the alignment of the SWUIS-A Xybion digital

NASA Technical Reports Server (NTRS)

2002-01-01

Southwest Research Institute astronomer Dan Durda checks the alignment of the SWUIS-A Xybion digital camera mounted in the rear cockpit of a NASA Dryden F/A-18B before taking off on an astronomy mission to search for small vulcanoids (asteroids) that may be orbiting between the sun and the planet Mercury.
Wavefront error measurement of the concave ellipsoidal mirrors of the METIS coronagraph on ESA Solar Orbiter mission

NASA Astrophysics Data System (ADS)

Sandri, P.

2017-12-01

The paper describes the alignment technique developed for the wavefront error measurement of ellipsoidal mirrors presenting a central hole. The achievement of a good alignment with a classic setup at the finite conjugates when mirrors are uncoated cannot be based on the identification and materialization at naked eye of the retro-reflected spot by the mirror under test as the intensity of the retro-reflected spot results to be ≈1E-3 of the intensity of the injected laser beam of the interferometer. We present the technique developed for the achievement of an accurate alignment in the setup at the finite conjugate even in condition of low intensity based on the use of an autocollimator adjustable in focus position and a small polished flat surface on the rear side of the mirror. The technique for the alignment has successfully been used for the optical test of the concave ellipsoidal mirrors of the METIS coronagraph of the ESA Solar Orbiter mission. The presented method results to be advantageous in terms of precision and of time saving also when the mirrors are reflective coated and integrated into their mechanical hardware.
Space shuttle navigation analysis. Volume 2: Baseline system navigation

NASA Technical Reports Server (NTRS)

Jones, H. L.; Luders, G.; Matchett, G. A.; Rains, R. G.

1980-01-01

Studies related to the baseline navigation system for the orbiter are presented. The baseline navigation system studies include a covariance analysis of the Inertial Measurement Unit calibration and alignment procedures, postflight IMU error recovery for the approach and landing phases, on-orbit calibration of IMU instrument biases, and a covariance analysis of entry and prelaunch navigation system performance.
The Smaller Alignment Index (SALI) applied in a study of stellar orbits in barred galaxies potential models using the LP-VIcode

NASA Astrophysics Data System (ADS)

Caritá, Lucas Antonio; Rodrigues, Irapuan; Puerari, Ivânio; Schiavo, Luiz Eduardo Camargo Aranha

2018-04-01

The Smaller Alignment Index (SALI) is a mathematical tool, not yet conventional, for chaos detection in the phase space of Hamiltonian Dynamical Systems. The SALI values has temporal behaviors very specific to ordered or chaotic motions, what makes the distinction between order and chaos easily observable in these systems. In this paper, this method will be applied to the stability study of stellar orbits immersed in gravitational potential of barred galaxies, since the motion of a test particle in a rotating barred galaxy model is given by a Hamiltonian function. Extracting four parameter sets from the Manos and Athanassoula (2011) work and elaborating a different initial conditions set for each case, we were able to introduce another point of view of their stability study for two degrees of freedom. We have also introduced two new extreme models that corroborates with the conclusions that more axisymmetric bars create an environment with less chaos and that more massive bars create an environment with more chaos. Separate studies were carried out for prograde and retrograde orbits that showed that the retrograde orbits seem more conducive to chaos. To perform all the orbits integrations we used the LP-VIcode program.
Effect of spaceflight on the spatial orientation of the vestibulo-ocular reflex during eccentric roll rotation: A case report.

PubMed

Reschke, Millard F; Wood, Scott J; Clément, Gilles

2018-01-01

Ground-based studies have reported shifts of the vestibulo-ocular reflex (VOR) slow phase velocity (SPV) axis toward the resultant gravito-inertial force vector. The VOR was examined during eccentric roll rotation before, during and after an 8-day orbital mission. On orbit this vector is aligned with the head z-axis. Our hypothesis was that eccentric roll rotation on orbit would generate horizontal eye movements. Two subjects were rotated in a semi-supine position with the head nasal-occipital axis parallel to the axis of rotation and 0.5 m off-center. The chair accelerated at 120 deg/s2 to 120 deg/s, rotated at constant velocity for one minute, and then decelerated to a stop in similar fashion. On Earth, the stimulation primarily generated torsional VOR. During spaceflight, in one subject torsional VOR became horizontal VOR, and then decayed very slowly. In the other subject, torsional VOR was reduced on orbit relative to pre- and post-flight, but the SPV axis did not rotate. We attribute the shift from torsional to horizontal VOR on orbit to a spatial orientation of velocity storage toward alignment with the gravito-inertial force vector, and the inter-individual difference to cognitive factors related to the subjective straight-ahead.
Halo Intrinsic Alignment: Dependence on Mass, Formation Time, and Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Qianli; Kang, Xi; Wang, Peng

In this paper we use high-resolution cosmological simulations to study halo intrinsic alignment and its dependence on mass, formation time, and large-scale environment. In agreement with previous studies using N -body simulations, it is found that massive halos have stronger alignment. For the first time, we find that for a given halo mass older halos have stronger alignment and halos in cluster regions also have stronger alignment than those in filaments. To model these dependencies, we extend the linear alignment model with inclusion of halo bias and find that the halo alignment with its mass and formation time dependence canmore » be explained by halo bias. However, the model cannot account for the environment dependence, as it is found that halo bias is lower in clusters and higher in filaments. Our results suggest that halo bias and environment are independent factors in determining halo alignment. We also study the halo alignment correlation function and find that halos are strongly clustered along their major axes and less clustered along the minor axes. The correlated halo alignment can extend to scales as large as 100 h {sup −1} Mpc, where its feature is mainly driven by the baryon acoustic oscillation effect.« less
ON THE TIDAL DISSIPATION OF OBLIQUITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, T. M.; Lin, D. N. C., E-mail: tami@lpl.arizona.edu, E-mail: lin@ucolick.org

2013-05-20

We investigate tidal dissipation of obliquity in hot Jupiters. Assuming an initial random orientation of obliquity and parameters relevant to the observed population, the obliquity of hot Jupiters does not evolve to purely aligned systems. In fact, the obliquity evolves to either prograde, retrograde, or 90 Degree-Sign orbits where the torque due to tidal perturbations vanishes. This distribution is incompatible with observations which show that hot Jupiters around cool stars are generally aligned. This calls into question the viability of tidal dissipation as the mechanism for obliquity alignment of hot Jupiters around cool stars.
Alignment effect of N2(A3Σu+) in the energy transfer reaction of aligned N2(A3Σu+) + NO(X2Π) → NO(A2Σ+) + N2(X1Σg+).

PubMed

Ohoyama, H; Maruyama, S

2012-06-28

Steric effect in the energy transfer reaction of N(2)(A(3)Σ(u)(+)) + NO(X(2)Π) → NO(A(2)Σ(+)) + N(2)(X(1)Σ(g)(+)) has been studied under crossed beam conditions at a collision energy of ~0.07 eV by using an aligned N(2)(A(3)Σ(u)(+)) beam prepared by a magnetic hexapole. The emission intensity of NO(A(2)Σ(+)) has been measured as a function of the magnetic orientation field direction (i.e., alignment of N(2)(A(3)Σ(u)(+))) in the collision frame. A significant alignment effect on the energy transfer probability is observed. The shape of the steric opacity function turns out to be most reactive at the oblique configuration of N(2)(A(3)Σ(u)(+)) with an orientation angle of γ(v(R)) ~ 45° with respect to the relative velocity vector (v(R)), which has a good correlation with the spatial distribution of the 2pπ(g)* molecular orbital of N(2)(A(3)Σ(u)(+)). We propose the electron exchange mechanism in which the energy transfer probability is dominantly controlled by the orbital overlap between N(2)(2pπ(g)*) and NO(6σ).
Some aspects of SR beamline alignment

NASA Astrophysics Data System (ADS)

Gaponov, Yu. A.; Cerenius, Y.; Nygaard, J.; Ursby, T.; Larsson, K.

2011-09-01

Based on the Synchrotron Radiation (SR) beamline optical element-by-element alignment with analysis of the alignment results an optimized beamline alignment algorithm has been designed and developed. The alignment procedures have been designed and developed for the MAX-lab I911-4 fixed energy beamline. It has been shown that the intermediate information received during the monochromator alignment stage can be used for the correction of both monochromator and mirror without the next stages of alignment of mirror, slits, sample holder, etc. Such an optimization of the beamline alignment procedures decreases the time necessary for the alignment and becomes useful and helpful in the case of any instability of the beamline optical elements, storage ring electron orbit or the wiggler insertion device, which could result in the instability of angular and positional parameters of the SR beam. A general purpose software package for manual, semi-automatic and automatic SR beamline alignment has been designed and developed using the developed algorithm. The TANGO control system is used as the middle-ware between the stand-alone beamline control applications BLTools, BPMonitor and the beamline equipment.
Orbital alignment at the internal interface of arylthiol functionalized CdSe molecular hybrids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhi; Schlaf, Rudy, E-mail: schlaf@usf.edu; Mazzio, Katherine A.

Organic-inorganic nanoparticle molecular hybrid materials are interesting candidates for improving exciton separation in organic solar cells. The orbital alignment at the internal interface of cadmium selenide (ArS-CdSe) hybrid materials functionalized with covalently attached arylthiolate moieties was investigated through X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A physisorbed interface between arylthiol (ArSH) ligands and CdSe nanoparticles was also investigated for comparison. This interface was created via a multi-step thin film deposition procedure in-vacuo, where the surface was characterized after each experimental step. This enabled the direct comparison of ArSH/CdSe interfaces produced via physisorption and ArS-CdSe covalently attached hybrid materials,more » which rely on a chemical reaction for their synthesis. All material depositions were performed using an electrospray deposition, which enabled the direct injection of solution-originating molecular species into the vacuum system. This method allows XPS and UPS measurements to be performed immediately after deposition without exposure to the atmosphere. Transmission electron microscopy was used to determine the morphology and particle size of the deposited materials. Ultraviolet-visible spectroscopy was used to estimate the optical band gap of the CdSe nanoparticles and the HOMO-LUMO gap of the ArSH ligands. These experiments showed that hybridization via covalent bonds results in an orbital realignment at the ArSH/CdSe interface in comparison to the physisorbed interface. The orbital alignment within the hybrid caused a favorable electron injection barrier, which likely facilitates exciton-dissociation while preventing charge-recombination.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuura, Yukihito, E-mail: matsuura@chem.nara-k.ac.jp

The tunneling magnetoresistance (TMR) of a silicon chain sandwiched between nickel electrodes was examined by using first-principles density functional theory. The relative orientation of the magnetization in a parallel-alignment (PA) configuration of two nickel electrodes enhanced the current with a bias less than 0.4 V compared with that in an antiparallel-alignment configuration. Consequently, the silicon chain-nickel electrodes yielded good TMR characteristics. In addition, there was polarized spin current in the PA configuration. The spin polarization of sulfur atoms functioning as a linking bridge between the chain and nickel electrode played an important role in the magnetic effects of the electric current.more » Moreover, the hybridization of the sulfur 3p orbital and σ-conjugated silicon 3p orbital contributed to increasing the total current.« less
ACCELERATORS: Beam based alignment of the SSRF storage ring

NASA Astrophysics Data System (ADS)

Zhang, Man-Zhou; Li, Hao-Hu; Jiang, Bo-Cheng; Liu, Gui-Min; Li, De-Ming

2009-04-01

There are 140 beam position monitors (BPMs) in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring used for measuring the closed orbit. As the BPM pickup electrodes are assembled directly on the vacuum chamber, it is important to calibrate the electrical center offset of the BPM to an adjacent quadrupole magnetic center. A beam based alignment (BBA) method which varies individual quadrupole magnet strength and observes its effects on the orbit is used to measure the BPM offsets in both the horizontal and vertical planes. It is a completely automated technique with various data processing methods. There are several parameters such as the strength change of the correctors and the quadrupoles which should be chosen carefully in real measurement. After several rounds of BBA measurement and closed orbit correction, these offsets are set to an accuracy better than 10 μm. In this paper we present the method of beam based calibration of BPMs, the experimental results of the SSRF storage ring, and the error analysis.
Target Assembly to Check Boresight Alignment of Active Sensors

NASA Technical Reports Server (NTRS)

Ramos-Izquierdo, Luis; Scott, V. Stanley; Riris, Haris; Cavanaugh, John; Liiva, Peter; Rodriguez, Michael

2011-01-01

A compact and portable target assembly (Fig. 1) has been developed to measure the boresite alignment of LRO's Lunar Orbiter Laser Altimeter (LOLA) instrument at the spacecraft level. The concept for this target assembly has evolved over many years with earlier versions used to test the Mars Observer Laser Altimeter (MOLA), the Geoscience Laser Altimeter System (GLAS), and the Mercury Laser Altimeter (MLA) space-based instruments.
Field-Aligned Currents in Saturn's Magnetosphere: Observations From the F-Ring Orbits

NASA Astrophysics Data System (ADS)

Hunt, G. J.; Provan, G.; Bunce, E. J.; Cowley, S. W. H.; Dougherty, M. K.; Southwood, D. J.

2018-05-01

We investigate the azimuthal magnetic field signatures associated with high-latitude field-aligned currents observed during Cassini's F-ring orbits (October 2016-April 2017). The overall ionospheric meridional current profiles in the northern and southern hemispheres, that is, the regions poleward and equatorward of the field-aligned currents, differ most from the 2008 observations. We discuss these differences in terms of the seasonal change between data sets and local time (LT) differences, as the 2008 data cover the nightside while the F-ring data cover the post-dawn and dusk sectors in the northern and southern hemispheres, respectively. The F-ring field-aligned currents typically have a similar four current sheet structure to those in 2008. We investigate the properties of the current sheets and show that the field-aligned currents in a hemisphere are modulated by that hemisphere's "planetary period oscillation" (PPO) systems. We separate the PPO-independent and PPO-related currents in both hemispheres using their opposite symmetry. The average PPO-independent currents peak at 1.5 MA/rad just equatorward of the open closed field line boundary, similar to the 2008 observations. However, the PPO-related currents in both hemispheres are reduced by 50% to 0.4 MA/rad. This may be evidence of reduced PPO amplitudes, similar to the previously observed weaker equatorial oscillations at similar dayside LTs. We do not detect the PPO current systems' interhemispheric component, likely a result of the weaker PPO-related currents and their closure within the magnetosphere. We also do not detect previously proposed lower latitude discrete field-aligned currents that act to "turn off" the PPOs.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Jason W.; Linscott, Ethan; Shporer, Avi, E-mail: jwbarnes@uidaho.edu

We model the asymmetry of the KOI-13.01 transit lightcurve assuming a gravity-darkened rapidly rotating host star in order to constrain the system's spin-orbit alignment and transit parameters. We find that our model can reproduce the Kepler lightcurve for KOI-13.01 with a sky-projected alignment of {lambda} = 23 Degree-Sign {+-} 4 Degree-Sign and with the star's north pole tilted away from the observer by 48 Degree-Sign {+-} 4 Degree-Sign (assuming M{sub *} = 2.05 M{sub Sun }). With both these determinations, we calculate that the net misalignment between this planet's orbit normal and its star's rotational pole is 56 Degree-Sign {+-}more » 4 Degree-Sign . Degeneracies in our geometric interpretation also allow a retrograde spin-orbit angle of 124 Degree-Sign {+-} 4 Degree-Sign . This is the first spin-orbit measurement to come from gravity darkening and is one of only a few measurements of the full (not just the sky-projected) spin-orbit misalignment of an extrasolar planet. We also measure accurate transit parameters incorporating stellar oblateness and gravity darkening: R{sub *} 1.756 {+-} 0.014 R{sub Sun }, R{sub p} = 1.445 {+-} 0.016 R{sub Jup}, and i = 85.{sup 0}9 {+-} 0.{sup 0}4. The new lower planetary radius falls within the planetary mass regime for plausible interior models for the transiting body. A simple initial calculation shows that KOI-13.01's circular orbit is apparently inconsistent with the Kozai mechanism having driven its spin-orbit misalignment; planet-planet scattering and stellar spin migration remain viable mechanisms. Future Kepler data will improve the precision of the KOI-13.01 transit lightcurve, allowing more precise determination of transit parameters and the opportunity to use the Photometric Rossiter-McLaughlin effect to resolve the prograde/retrograde orbit determination degeneracy.« less
Design and Verification of Space Station EVA-Operated Truss Attachment System

NASA Technical Reports Server (NTRS)

Katell, Gabriel

2001-01-01

This paper describes the design and verification of a system used to attach two segments of the International Space Station (ISS). This system was first used in space to mate the P6 and Z1 trusses together in December 2000, through a combination of robotic and extravehicular tasks. Features that provided capture, coarse alignment, and fine alignment during the berthing process are described. Attachment of this high value hardware was critical to the ISS's sequential assembly, necessitating the inclusion of backup design and operational features. Astronauts checked for the proper performance of the alignment and bolting features during on-orbit operations. During berthing, the system accommodates truss-to-truss relative displacements that are caused by manufacturing tolerances and on-orbit thermal gradients. After bolt installation, the truss interface becomes statically determinate with respect to in-plane shear loads and isolates attach bolts from bending moments. The approach used to estimate relative displacements and the means of accommodating them is explained. Confidence in system performance was achieved through a cost-effective collection of tests and analyses, including thermal, structural, vibration, misalignment, contact dynamics, underwater simulation, and full-scale functional testing. Design considerations that have potential application to other mechanisms include accommodating variations of friction coefficients in the on-orbit joints, wrench torque tolerances, joint preload, moving element clearances at temperature extremes, and bolt-nut torque reaction.
Distinguishing spin-aligned and isotropic black hole populations with gravitational waves.

PubMed

Farr, Will M; Stevenson, Simon; Miller, M Coleman; Mandel, Ilya; Farr, Ben; Vecchio, Alberto

2017-08-23

The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins. Binary systems that formed through dynamical interactions between already-compact objects are expected to have isotropic spin orientations (that is, the spins of the black holes are randomly oriented with respect to the orbit of the binary system), whereas those that formed from pairs of stars born together are more likely to have spins that are preferentially aligned with the orbit. The best-measured combination of spin parameters for each of the four likely binary black hole detections GW150914, LVT151012, GW151226 and GW170104 is the 'effective' spin. Here we report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10 -7 against alignment. The existing preference for either an isotropic spin distribution or low spin magnitudes for the observed systems will be confirmed (or overturned) confidently in the near future.
Optimizing Parking Orbits for Roundtrip Mars Missions

NASA Technical Reports Server (NTRS)

Qu, Min; Merill, Raymond G.; Chai, Patrick; Komar, David R.

2017-01-01

A roundtrip Mars mission presents many challenges to the design of a transportation system and requires a series of orbital maneuvers within Mars vicinity to capture, reorient, and then return the spacecraft back to Earth. The selection of a Mars parking orbit is crucial to the mission design; not only can the parking or-bit choice drastically impact the ?V requirements of these maneuvers but also it must be properly aligned to target desired surface or orbital destinations. This paper presents a method that can optimize the Mars parking orbits given the arrival and departure conditions from heliocentric trajectories, and it can also en-force constraints on the parking orbits to satisfy other architecture design requirements such as co-planar subperiapsis descent to planned landing sites, due east or co-planar ascent back to the parking orbit, or low cost transfers to and from Phobos and Deimos.

Theory of Covalent Adsorbate Frontier Orbital Energies on Functionalized Light-Absorbing Semiconductor Surfaces.

PubMed

Yu, Min; Doak, Peter; Tamblyn, Isaac; Neaton, Jeffrey B

2013-05-16

Functional hybrid interfaces between organic molecules and semiconductors are central to many emerging information and solar energy conversion technologies. Here we demonstrate a general, empirical parameter-free approach for computing and understanding frontier orbital energies - or redox levels - of a broad class of covalently bonded organic-semiconductor surfaces. We develop this framework in the context of specific density functional theory (DFT) and many-body perturbation theory calculations, within the GW approximation, of an exemplar interface, thiophene-functionalized silicon (111). Through detailed calculations taking into account structural and binding energetics of mixed-monolayers consisting of both covalently attached thiophene and hydrogen, chlorine, methyl, and other passivating groups, we quantify the impact of coverage, nonlocal polarization, and interface dipole effects on the alignment of the thiophene frontier orbital energies with the silicon band edges. For thiophene adsorbate frontier orbital energies, we observe significant corrections to standard DFT (∼1 eV), including large nonlocal electrostatic polarization effects (∼1.6 eV). Importantly, both results can be rationalized from knowledge of the electronic structure of the isolated thiophene molecule and silicon substrate systems. Silicon band edge energies are predicted to vary by more than 2.5 eV, while molecular orbital energies stay similar, with the different functional groups studied, suggesting the prospect of tuning energy alignment over a wide range for photoelectrochemistry and other applications.
Atomic-scale visualization of surface-assisted orbital order

PubMed Central

Kim, Howon; Yoshida, Yasuo; Lee, Chi-Cheng; Chang, Tay-Rong; Jeng, Horng-Tay; Lin, Hsin; Haga, Yoshinori; Fisk, Zachary; Hasegawa, Yukio

2017-01-01

Orbital-related physics attracts growing interest in condensed matter research, but direct real-space access of the orbital degree of freedom is challenging. We report a first, real-space, imaging of a surface-assisted orbital ordered structure on a cobalt-terminated surface of the well-studied heavy fermion compound CeCoIn5. Within small tip-sample distances, the cobalt atoms on a cleaved (001) surface take on dumbbell shapes alternatingly aligned in the [100] and [010] directions in scanning tunneling microscopy topographies. First-principles calculations reveal that this structure is a consequence of the staggered dxz-dyz orbital order triggered by enhanced on-site Coulomb interaction at the surface. This so far overlooked surface-assisted orbital ordering may prevail in transition metal oxides, heavy fermion superconductors, and other materials. PMID:28948229
POET: A Model for Planetary Orbital Evolution Due to Tides on Evolving Stars

NASA Astrophysics Data System (ADS)

Penev, Kaloyan; Zhang, Michael; Jackson, Brian

2014-06-01

We make publicly available an efficient, versatile, easy to use and extend tool for calculating the evolution of circular aligned planetary orbits due to the tidal dissipation in the host star. This is the first model to fully account for the evolution of the angular momentum of the stellar convective envelope by the tidal coupling, the transfer of angular momentum between the stellar convective and radiative zones, the effects of the stellar evolution on the tidal dissipation efficiency and stellar core and envelope spins, the loss of stellar convective zone angular momentum to a magnetically launched wind and frequency dependent tidal dissipation. This is only a first release and further development is under way to allow calculating the evolution of inclined and eccentric orbits, with the latter including the tidal dissipation in the planet and its feedback on planetary structure. Considerable effort has been devoted to providing extensive documentation detailing both the usage and the complete implementation details, in order to make it as easy as possible for independent groups to use and/or extend the code for their purposes. POET represents a significant improvement over some previous models for planetary tidal evolution and so has many astrophysical applications. In this article, we describe and illustrate several key examples.
CONDITIONS OF PASSAGE AND ENTRAPMENT OF TERRESTRIAL PLANETS IN SPIN-ORBIT RESONANCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarov, Valeri V., E-mail: vvm@usno.navy.mil

The dynamical evolution of terrestrial planets resembling Mercury in the vicinity of spin-orbit resonances is investigated using comprehensive harmonic expansions of the tidal torque taking into account the frequency-dependent quality factors and Love numbers. The torque equations are integrated numerically with a small step in time, including the oscillating triaxial torque components but neglecting the layered structure of the planet and assuming a zero obliquity. We find that a Mercury-like planet with a current value of orbital eccentricity (0.2056) is always captured in 3:2 resonance. The probability of capture in the higher 2:1 resonance is approximately 0.23. These results aremore » confirmed by a semi-analytical estimation of capture probabilities as functions of eccentricity for both prograde and retrograde evolutions of spin rate. As follows from analysis of equilibrium torques, entrapment in 3:2 resonance is inevitable at eccentricities between 0.2 and 0.41. Considering the phase space parameters at the times of periastron, the range of spin rates and phase angles for which an immediate resonance passage is triggered is very narrow, and yet a planet like Mercury rarely fails to align itself into this state of unstable equilibrium before it traverses 2:1 resonance.« less
Orbital assembly and maintenance study

NASA Technical Reports Server (NTRS)

Gorman, D.; Grant, C.; Kyrias, G.; Lord, C.; Rombach, J.; Salis, M.; Skidmore, R.; Thomas, R.

1975-01-01

The requirements, conceptual design, tradeoffs, procedures, and techniques for orbital assembly of the support structure of the microwave power transmission system and the radio astronomy telescope are described. Thermal and stress analyses, packaging, alignment, and subsystems requirements are included along with manned vs. automated and transportation tradeoffs. Technical and operational concepts for the manned and automated maintenance of satellites were investigated and further developed results are presented.
Space Technology 5 Observations of Auroral Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Slavin, James

2008-01-01

During its three month long technology validation mission, Space Technology 5 (ST-5) returned high quality multi-point measurements of the near-Earth magnetic field. Its three micro-satellites were launched into a 300 x 4500 km, dawn - dusk, sun synchronous orbit (inclination = 105.60) orbit with a period of 138 min by a Pegasus launch vehicle on March 22, 2006. The spacecraft were maintained in a "pearls on a sting" constellation with controlled spacings ranging from just over 5000 km down to under 50 km. The individual micro-satellites were 48 cm tall octagons with diameters of 50 cm. They were spin-stabilized at approximately 20 rpm at deployment and slowly spun-down to about 15 rpm by the end of the mission. Each spacecraft carried a miniature tri-axial fluxgate magnetometer (MAG) provided by the University of California at Los Angeles mounted at the end of a ultra-low mass 72 cm boom. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness. and current density. Two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit are demonstrated: 1) the -standard method." based upon s/c velocity, but corrected for FAC current sheet motion. and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data sct and expand to include horizontal ionospheric currents. ULF waves and geomagnetic field gradient analyses.
Structural Analysis Peer Review for the Static Display of the Orbiter Atlantis at the Kennedy Space Center Visitors Center

NASA Technical Reports Server (NTRS)

Minute, Stephen A.

2013-01-01

Mr. Christopher Miller with the Kennedy Space Center (KSC) NASA Safety & Mission Assurance (S&MA) office requested the NASA Engineering and Safety Center's (NESC) technical support on March 15, 2012, to review and make recommendations on the structural analysis being performed for the Orbiter Atlantis static display at the KSC Visitor Center. The principal focus of the assessment was to review the engineering firm's structural analysis for lifting and aligning the orbiter and its static display configuration
The MAGIC of CINEMA: first in-flight science results from a miniaturised anisotropic magnetoresistive magnetometer

NASA Astrophysics Data System (ADS)

Archer, M. O.; Horbury, T. S.; Brown, P.; Eastwood, J. P.; Oddy, T. M.; Whiteside, B. J.; Sample, J. G.

2015-06-01

We present the first in-flight results from a novel miniaturised anisotropic magnetoresistive space magnetometer, MAGIC (MAGnetometer from Imperial College), aboard the first CINEMA (CubeSat for Ions, Neutrals, Electrons and MAgnetic fields) spacecraft in low Earth orbit. An attitude-independent calibration technique is detailed using the International Geomagnetic Reference Field (IGRF), which is temperature dependent in the case of the outboard sensor. We show that the sensors accurately measure the expected absolute field to within 2% in attitude mode and 1% in science mode. Using a simple method we are able to estimate the spacecraft's attitude using the magnetometer only, thus characterising CINEMA's spin, precession and nutation. Finally, we show that the outboard sensor is capable of detecting transient physical signals with amplitudes of ~ 20-60 nT. These include field-aligned currents at the auroral oval, qualitatively similar to previous observations, which agree in location with measurements from the DMSP (Defense Meteorological Satellite Program) and POES (Polar-orbiting Operational Environmental Satellites) spacecraft. Thus, we demonstrate and discuss the potential science capabilities of the MAGIC instrument onboard a CubeSat platform.
Stability of Multi-Planet Systems Orbiting in the Alpha Centauri AB System

NASA Astrophysics Data System (ADS)

Lissauer, Jack

2018-04-01

We evaluate how closely-spaced planetary orbits in multiple planet systems can be and still survive for billion-year timescales within the alpha Centauri AB system. Although individual planets on nearly circular, coplanar orbits can survive throughout the habitable zones of both stars, perturbations from the companion star imply that the spacing of such planets in multi-planet systems must be significantly larger than the spacing of similar systems orbiting single stars in order to be long-lived. Because the binary companion induces a forced eccentricity upon circumstellar planets, stable orbits with small initial eccentricities aligned with the binary orbit are possible to slightly larger initial semimajor axes than are initially circular orbits. Initial eccentricities close to the appropriate forced eccentricity can have a much larger affect on how closely planetary orbits can be spaced, on how many planets may remain in the habitable zones, although the required spacing remains significantly higher than for planets orbiting single stars.
Distinguishing black-hole spin-orbit resonances by their gravitational-wave signatures

NASA Astrophysics Data System (ADS)

Gerosa, Davide; O'Shaughnessy, Richard; Kesden, Michael; Berti, Emanuele; Sperhake, Ulrich

2014-06-01

If binary black holes form following the successive core collapses of sufficiently massive binary stars, precessional dynamics may align their spins, Smathvariant="bold">1 and Smathvariant="bold">2, and the orbital angular momentum L into a plane in which they jointly precess about the total angular momentum J. These spin orientations are known as spin-orbit resonances since S1, S2, and L all precess at the same frequency to maintain their planar configuration. Two families of such spin-orbit resonances exist, differentiated by whether the components of the two spins in the orbital plane are either aligned or antialigned. The fraction of binary black holes in each family is determined by the stellar evolution of their progenitors, so if gravitational-wave detectors could measure this fraction they could provide important insights into astrophysical formation scenarios for binary black holes. In this paper, we show that even under the conservative assumption that binary black holes are observed along the direction of J (where precession-induced modulations to the gravitational waveforms are minimized), the waveforms of many members of each resonant family can be distinguished from all members of the other family in events with signal-to-noise ratios ρ ≃10, typical of those expected for the first detections with Advanced LIGO and Virgo. We hope that our preliminary findings inspire a greater appreciation of the capability of gravitational-wave detectors to constrain stellar astrophysics and stimulate further studies of the distinguishability of spin-orbit resonant families in more expanded regions of binary black-hole parameter space.
In-orbit verification of MHS spectral channels co-registration using the moon

NASA Astrophysics Data System (ADS)

Bonsignori, Roberto

2017-09-01

In-orbit verification of the co-registration of channels in a scanning microwave or infrared radiometer can in principle be done during normal in-orbit operation, by using the regular events of lunar intrusion in the instrument cold space calibration view. A technique of data analysis based on best fit of data across lunar intrusions has been used to check the mutual alignment of the spectral channels of the MHS instrument. MHS (Microwave Humidity Sounder) is a cross-track scanning radiometer in the millimetre-wave range flying on EUMETSAT and NOAA polar satellites, used operationally for the retrieval of atmospheric parameters in numerical weather prediction and nowcasting. This technique does not require any special operation or manoeuvre and only relies on analysis of data from the nominal scanning operation. The co-alignment of sounding channels and window channels can be evaluated by this technique, which would not be possible by using earth landmarks, due to the absorption effect of the atmosphere. The analysis reported in this paper shows an achievable accuracy below 0.5 mrad against a beam width at 3dB and spatial sampling interval of about 20 mrad. In-orbit results for the MHS instrument on Metop-B are also compared with the pre-launch instrument characterisation, showing a good correlation.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirano, Teruyuki; Sanchis-Ojeda, Roberto; Winn, Joshua N.

We present a test for spin-orbit alignment for the host stars of 25 candidate planetary systems detected by the Kepler spacecraft. The inclination angle of each star's rotation axis was estimated from its rotation period, rotational line broadening, and radius. The rotation periods were determined using the Kepler photometric time series. The rotational line broadening was determined from high-resolution optical spectra with the Subaru High Dispersion Spectrograph. Those same spectra were used to determine the star's photospheric parameters (effective temperature, surface gravity, metallicity), which were then interpreted with stellar-evolutionary models to determine stellar radii. We combine the new sample withmore » the seven stars from our previous work on this subject, finding that the stars show a statistical tendency to have inclinations near 90°, in alignment with the planetary orbits. Possible spin-orbit misalignments are seen in several systems, including three multiple-planet systems (KOI-304, 988, 2261). Ideally, these systems should be scrutinized with complementary techniques, such as the Rossiter-McLaughlin effect, starspot-crossing anomalies, or asteroseismology, but the measurements will be difficult owing to the relatively faint apparent magnitudes and small transit signals in these systems.« less
Orbital docking system centerline color television camera system test

NASA Technical Reports Server (NTRS)

Mongan, Philip T.

1993-01-01

A series of tests was run to verify that the design of the centerline color television camera (CTVC) system is adequate optically for the STS-71 Space Shuttle Orbiter docking mission with the Mir space station. In each test, a mockup of the Mir consisting of hatch, docking mechanism, and docking target was positioned above the Johnson Space Center's full fuselage trainer, which simulated the Orbiter with a mockup of the external airlock and docking adapter. Test subjects viewed the docking target through the CTVC under 30 different lighting conditions and evaluated target resolution, field of view, light levels, light placement, and methods of target alignment. Test results indicate that the proposed design will provide adequate visibility through the centerline camera for a successful docking, even with a reasonable number of light failures. It is recommended that the flight deck crew have individual switching capability for docking lights to provide maximum shadow management and that centerline lights be retained to deal with light failures and user preferences. Procedures for light management should be developed and target alignment aids should be selected during simulated docking runs.
Mission design for a halo orbiter of the earth

NASA Technical Reports Server (NTRS)

Farquhar, R. W.; Muhonen, D. P.; Richardson, D. L.

1976-01-01

The International Sun-Earth Explorer (ISEE) scientific satellite to be stationed in 1978 in the vicinity of the sun-earth interior libration point to continuously monitor the space between the sun and the earth, including the distant geomagnetic tail is described. Orbit selection considerations for the ISEE-C are discussed along with stationkeeping requirements and fuel-optimal trajectories. Due to the alignment of the interior libration point with the sun as viewed from the earth, it will be necessary to place the satellite into a 'halo orbit' around the libration point, in order to eliminate solar interference with down-link telemetry. Parametric data for transfer trajectories between an earth parking orbit (altitude about 185 km) and a libration-point orbit are presented. It is shown that the insertion magnitude required for placing a satellite into an acceptable halo orbit is rather modest.
Relationships between field-aligned currents, electric fields, and particle precipitation as observed by Dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1984-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.
Relationships between field-aligned currents, electric fields and particle precipitation as observed by dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1983-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.
Energy Level Alignment at the Interface between Linear-Structured Benzenediamine Molecules and Au(111) Surface

NASA Astrophysics Data System (ADS)

Li, Guo; Rangel, Tonatiuh; Liu, Zhenfei; Cooper, Valentino; Neaton, Jeffrey

Using density functional theory with model self-energy corrections, we calculate the adsorption energetics and geometry, and the energy level alignment of benzenediamine (BDA) molecules adsorbed on Au(111) surfaces. Our calculations show that linear structures of BDA, stabilized via hydrogen bonds between amine groups, are energetically more favorable than monomeric phases. Moreover, our self-energy-corrected calculations of energy level alignment show that the highest occupied molecular orbital energy of the BDA linear structure is deeper relative to the Fermi level relative to the isolated monomer and agrees well with the values measured with photoemission spectroscopy. This work supported by DOE.
Brassboard Astrometric Beam Combiner (ABC) Development for the Space Interferometry Mission (SIM)

NASA Technical Reports Server (NTRS)

Jeganathan, Muthu; Kuan, Gary; Rud, Mike; Lin, Sean; Sutherland, Kristen; Moore, James; An, Xin

2008-01-01

The Astrometric Beam Combiner (ABC) is a critical element of the Space Interferometry Mission (SIM) that performs three key functions: coherently combine starlight from two siderostats; individually detect starlight for angle tracking; and disperse and detect the interferometric fringes. In addition, the ABC contains: a stimulus, cornercubes and shutters for in-orbit calibration; several tip/tilt mirror mechanisms for in-orbit alignment; and internal metrology beam launcher for pathlength monitoring. The detailed design of the brassboard ABC (which has the form, fit and function of the flight unit) is complete, procurement of long-lead items is underway, and assembly and testing is expected to be completed in Spring 2009. In this paper, we present the key requirements for the ABC, details of the completed optical and mechanical design as well as plans for assembly and alignment.
Lunar shadow eclipse prediction models for the Earth orbiting spacecraft: Comparison and application to LEO and GEO spacecrafts

NASA Astrophysics Data System (ADS)

Srivastava, Vineet K.; Kumar, Jai; Kulshrestha, Shivali; Srivastava, Ashutosh; Bhaskar, M. K.; Kushvah, Badam Singh; Shiggavi, Prakash; Vallado, David A.

2015-05-01

A solar eclipse occurs when the Sun, Moon and Earth are aligned in such a way that shadow of the Moon falls on the Earth. The Moon's shadow also falls on the Earth orbiting spacecraft. In this case, the alignment of the Sun, Moon, and spacecraft is similar to that of the Sun, Moon, and Earth but this phenomenon is often referred as a lunar eclipse falling on the spacecraft. Lunar eclipse is not as regular in terms of times of occurrence, duration, and depth as the Earth shadow eclipse and number of its occurrence per orbital location per year ranges from zero to four with an average of two per year; a spacecraft may experience two to three lunar eclipses within a twenty-four hour period [2]. These lunar eclipses can cause severe spacecraft operational problems. This paper describes two lunar shadow eclipse prediction models using a projection map approach and a line of intersection method by extending the Earth shadow eclipse models described by Srivastava et al. [10,11] for the Earth orbiting spacecraft. The attractive feature of both models is that they are much easier to implement. Both mathematical models have been simulated for two Indian low Earth orbiting spacecrafts: Oceansat-2, Saral-1, and two geostationary spacecrafts: GSAT-10, INSAT-4CR. Results obtained by the models compare well with lunar shadow model given by Escobal and Robertson [12], and high fidelity commercial software package, Systems Tool Kit (STK) of AGI.
A synoptic study of the nature and effects of field aligned low energy electron precipitation in the auroral regions. Ph.D. Thesis - Catholic Univ. of America

NASA Technical Reports Server (NTRS)

Berko, F. W.

1972-01-01

A synoptic study is presented of field-aligned precipitation events observed during a 16-month period, representing a full 4 pi precession of the satellite orbital plane in magnetic local time. The morphology of this type of precipitation, its nature, and relationships between this phenomenon and other geophysical events are discussed in the context of the 16-month data base.

Numerical study on exciton transport and light emission for organic light emitting diodes with an emission layer.

PubMed

Kim, K S; Hwang, Y W; Won, T Y

2013-12-01

This paper reports the results of a numerical study on carrier injection and exciton transport in an organic light emitting diode (OLED) structure based on tris (8-hydroxyquinolinato) aluminum (Alq3). Because charge accumulation at the interfaces between the emission layer (EML) and transport layer are believed to increase the recombination rate, which also increases the exciton density, a numerical study was performed on the effect of inserting an EML in the bilayer structure. In the first case considered, the lowest unoccupied molecular orbital (LUMO) of the EML was aligned with the LUMO of the hole transport layer (HTL), whereas the highest occupied molecular orbital (HOMO) of the EML was aligned with the HOMO of the electron transport layer (ETL). In the second case, the LUMO of the EML was aligned with the LUMO of the ETL and the HOMO of the EML was aligned with the HOMO of the HTL. In case of a charge-blocking device, most of the recombination appeared to occur at both edges of the EML because the electric field exhibited a peak in these areas. On the other hand, in the case of the charge-confining device, the electric field was confined at the interface between the EML and ETL. This paper also discussed the effect of the insertion of a doping layer as transport layer.
Exoplanetary Spin-Orbit Alignment: Results from the Ensemble of Rossiter-McLaughlin Measurements

NASA Technical Reports Server (NTRS)

Fabrycky, Daniel C.; Winn, Joshua N.

2009-01-01

One possible diagnostic of planet formation, orbital migration, and tidal evolution is the angle between a planet's orbital axis and the spin axis of its parent star. In general, Psi cannot be measured, but for transiting planets one can measure the angle lambda between the sky projections of the two axes via the Rossiter-McLaughlin effect. In this paper we showed how to combine measurements of lambda in different systems to derive statistical constraints on Psi, using a Bayesian analysis. The results provided evidence for two distinct modes of planet migration.
Novel Models of Visual Topographic Map Alignment in the Superior Colliculus

PubMed Central

El-Ghazawi, Tarek A.; Triplett, Jason W.

2016-01-01

The establishment of precise neuronal connectivity during development is critical for sensing the external environment and informing appropriate behavioral responses. In the visual system, many connections are organized topographically, which preserves the spatial order of the visual scene. The superior colliculus (SC) is a midbrain nucleus that integrates visual inputs from the retina and primary visual cortex (V1) to regulate goal-directed eye movements. In the SC, topographically organized inputs from the retina and V1 must be aligned to facilitate integration. Previously, we showed that retinal input instructs the alignment of V1 inputs in the SC in a manner dependent on spontaneous neuronal activity; however, the mechanism of activity-dependent instruction remains unclear. To begin to address this gap, we developed two novel computational models of visual map alignment in the SC that incorporate distinct activity-dependent components. First, a Correlational Model assumes that V1 inputs achieve alignment with established retinal inputs through simple correlative firing mechanisms. A second Integrational Model assumes that V1 inputs contribute to the firing of SC neurons during alignment. Both models accurately replicate in vivo findings in wild type, transgenic and combination mutant mouse models, suggesting either activity-dependent mechanism is plausible. In silico experiments reveal distinct behaviors in response to weakening retinal drive, providing insight into the nature of the system governing map alignment depending on the activity-dependent strategy utilized. Overall, we describe novel computational frameworks of visual map alignment that accurately model many aspects of the in vivo process and propose experiments to test them. PMID:28027309
Orbital-dependent density functionals: Theory and applications

NASA Astrophysics Data System (ADS)

Kümmel, Stephan; Kronik, Leeor

2008-01-01

This review provides a perspective on the use of orbital-dependent functionals, which is currently considered one of the most promising avenues in modern density-functional theory. The focus here is on four major themes: the motivation for orbital-dependent functionals in terms of limitations of semilocal functionals; the optimized effective potential as a rigorous approach to incorporating orbital-dependent functionals within the Kohn-Sham framework; the rationale behind and advantages and limitations of four popular classes of orbital-dependent functionals; and the use of orbital-dependent functionals for predicting excited-state properties. For each of these issues, both formal and practical aspects are assessed.
Internal Tide Generation by Tall Ocean Ridges

DTIC Science & Technology

2009-09-01

Earth - sun and the Earth -moon orbits . As the earth and the moon rotate, so does the alignment of the tidal forces, such...tidal periods. It has since become recognized that internal tides are part of important global energy systems: the orbits of the moon around the Earth ...and the Earth around the sun , and the energy budget of the ocean. For instance, the energy in the moon- Earth system is decreasing, such that every
Fabrication and material properties of fibrous PHBV scaffolds depending on the cross-ply angle for tissue engineering.

PubMed

Kim, Yang-Hee; Min, Young-Ki; Lee, Byong-Taek

2012-11-01

Fibrous PHBV cross-ply scaffolds were fabricated using the electrospinning technique. The electrospun fibers were arranged depending on angles of alignment, which were 180°, 90°, 60°, and 45°. The stress and strain values of the fibrous PHBV cross-ply scaffolds increased as the cross-ply angle increased. At 180°, the strength and strain values of the fibers depended on tensile loading directions. At an alignment of 90°, the PHBV scaffolds had a stress value of 3.5 MPa, which was more than two times higher than the random structure. The cell morphology and proliferation of L-929 cells was strongly dependant on the fiber alignment and the best results were observed when the angle alignment was high. The results of this study showed that the cross-ply structure of the PHBV scaffold affected not only the cell adhesion and spreading properties but also dictated the mechanical properties, which were dependent on the angles of alignment.
Autonomous orbital navigation using Kepler's equation

NASA Technical Reports Server (NTRS)

Boltz, F. W.

1974-01-01

A simple method of determining the six elements of elliptic satellite orbits has been developed for use aboard manned and unmanned spacecraft orbiting the earth, moon, or any planet. The system requires the use of a horizon sensor or other device for determining the local vertical, a precision clock or timing device, and Apollo-type navigation equipment including an inertial measurement unit (IMU), a digital computer, and a coupling data unit. The three elements defining the in-plane motion are obtained from simultaneous measurements of central angle traversed around the planet and elapsed flight time using a linearization of Kepler's equation about a reference orbit. It is shown how Kalman filter theory may also be used to determine the in-plane orbital elements. The three elements defining the orbit orientation are obtained from position angles in celestial coordinates derived from the IMU with the spacecraft vertically oriented after alignment of the IMU to a known inertial coordinate frame.
Communication: Photoionization of degenerate orbitals for randomly oriented molecules: The effect of time-reversal symmetry on recoil-ion momentum angular distributions

NASA Astrophysics Data System (ADS)

Suzuki, Yoshi-Ichi

2018-04-01

The photoelectron asymmetry parameter β, which characterizes the direction of electrons ejected from a randomly oriented molecular ensemble by linearly polarized light, is investigated for degenerate orbitals. We show that β is totally symmetric under the symmetry operation of the point group of a molecule, and it has mixed properties under time reversal. Therefore, all degenerate molecular orbitals, except for the case of degeneracy due to time reversal, have the same β (Wigner-Eckart theorem). The exceptions are e-type complex orbitals of the Cn, Sn, Cnh, T, and Th point groups, and calculations on boric acid (C3h symmetry) are performed as an example. However, including those point groups, all degenerate orbitals have the same β if those orbitals are real. We discuss the implications of this operator formalism for molecular alignment and photoelectron circular dichroism.
Significant initial results from the environmental measurements experiment on ATS-6

NASA Technical Reports Server (NTRS)

Fritz, T. A.; Arthur, C. W.; Blake, J. B.; Coleman, P. J., Jr.; Corrigan, J. P.; Cummings, W. D.; Deforest, S. E.; Erickson, K. N.; Konradi, A.; Lennartsson, W.

1977-01-01

The Applications Technology Satellite (ATS-6), launched into synchronous orbit on 30 May 1974, carried a set of six particle detectors and a triaxial fluxgate magnetometer. The particle detectors were able to determine the ion and electron distribution functions from 1 to greater than 10 to the 8th power eV. It was found that the magnetic field is weaker and more tilted than predicted by models which neglect internal plasma and that there is a seasonal dependence to the magnitude and tilt. ATS-6 magnetic field measurements showed the effects of field-aligned currents associated with substorms, and large fluxes of field-aligned particles were observed with the particle detectors. Encounters with the plasmasphere revealed the existence of warm plasma with temperatures up to 30 eV. A variety of correlated waves in both the particles and fields were observed: pulsation continuous oscillations, seen predominantly in the plasmasphere bulge; ultralow frequency (ULF) standing waves; ring current proton ULF waves; and low frequency waves that modulate the energetic electrons. In additon, large scale waves on the energetic-ion-trapping boundary were observed, and the intensity of energetic electrons was modulated in association with the passage of sector boundaries of the interplanetary magnetic field.
Field-aligned electrostatic potential differences on the Martian night side

NASA Astrophysics Data System (ADS)

Lillis, Rob; Collinson, Glyn; Mitchell, David

2017-04-01

Field-aligned electrostatic potential differences on the Martian night side above 170 km can be inferred with the aid of a kinetic electron transport model and in a statistical sense, by energy-dependent angular shifts in electron loss cones measured in Mars orbit. Potentials between 170 km and 400 km derived from pitch angle distributions measured by the Mars Global Surveyor (MGS) Magnetometer/ Electron Reflectometer experiment (MAG/ER) at 2 a.m. local time are typically small (-10 V to 10 V) but can reach magnitudes of >100 V. Geographically, the strongest negative potential differences (with mean values up to -50 V) are preferentially observed at the boundaries between open and closed strong magnetic field regions, while positive potential differences are preferentially observed further from open field lines. These characteristics may reflect current systems closing at high altitude through cross-tail currents and at low altitude in the conducting night side ionosphere. We will present a synthesis of potentials derived from pitch angle distributions measured by both MGS MAG/ER as mentioned above, and by the MAVEN Solar Wind Electron Analyzer (SWEA) collected at a range of local times and altitudes.
An initial ULF wave index derived from 2 years of Swarm observations

NASA Astrophysics Data System (ADS)

Papadimitriou, Constantinos; Balasis, Georgios; Daglis, Ioannis A.; Giannakis, Omiros

2018-03-01

The ongoing Swarm satellite mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. Herein, we use a new methodological approach for the detection and classification of ultra low-frequency (ULF) wave events observed by Swarm based on an existing time-frequency analysis (TFA) tool and utilizing a state-of-the-art high-resolution magnetic field model and Swarm Level 2 products (i.e., field-aligned currents - FACs - and the Ionospheric Bubble Index - IBI). We present maps of the dependence of ULF wave power with magnetic latitude and magnetic local time (MLT) as well as geographic latitude and longitude from the three satellites at their different locations in low-Earth orbit (LEO) for a period spanning 2 years after the constellation's final configuration. We show that the inclusion of the Swarm single-spacecraft FAC product in our analysis eliminates all the wave activity at high altitudes, which is physically unrealistic. Moreover, we derive a Swarm orbit-by-orbit Pc3 wave (20-100 MHz) index for the topside ionosphere and compare its values with the corresponding variations of solar wind variables and geomagnetic activity indices. This is the first attempt, to our knowledge, to derive a ULF wave index from LEO satellite data. The technique can be potentially used to define a new Level 2 product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications.
Satellite Alignment. I. Distribution of Substructures and their Dependence on Assembly History from N-body Simulations

NASA Astrophysics Data System (ADS)

Wang, Y. O.; Lin, W. P.; Kang, X.; Dutton, Aaron; Yu, Yu; Macciò, Andrea V.

2014-05-01

Observations have shown that the spatial distribution of satellite galaxies is not random, but aligned with the major axes of central galaxies. This alignment is dependent on galaxy properties, such that red satellites are more strongly aligned than blue satellites. Theoretical work conducted to interpret this phenomenon has found that it is due to the non-spherical nature of dark matter halos. However, most studies overpredict the alignment signal under the assumption that the central galaxy shape follows the shape of the host halo. It is also not clear whether the color dependence of alignment is due to an assembly bias or an evolution effect. In this paper we study these problems using a cosmological N-body simulation. Subhalos are used to trace the positions of satellite galaxies. It is found that the shapes of dark matter halos are mis-aligned at different radii. If the central galaxy shares the same shape as the inner host halo, then the alignment effect is weaker and agrees with observational data. However, it predicts almost no dependence of alignment on the color of satellite galaxies, though the late accreted subhalos show stronger alignment with the outer layer of the host halo than their early accreted counterparts. We find that this is due to the limitation of pure N-body simulations where satellite galaxies without associated subhalos ("orphan galaxies") are not resolved. These orphan (mostly red) satellites often reside in the inner region of host halos and should follow the shape of the host halo in the inner region.
Alignment relaxation of Ne*(2pi [J = 1]) atoms in He-Ne* glow discharges

NASA Astrophysics Data System (ADS)

Bahrim, Cristian; Khadilkar, Vaibhav; Matsukuma, Hiraku; Hasuo, Masahiro

2009-11-01

Alignment relaxation of the Ne*(2p5 3p; 2pi [J = 1]) atoms (where i = 2, 5, 7 or 10) induced by collisions with He atoms in glow discharges at 77 K < T < 1,000 K are reported. Close-coupling many-channel quantum calculations using a model potential for the Ne*(2p5 3p) - He system are compared with measurements of the alignment relaxation using the LIFS technique and the Hanle effect. The addition of the dipole polarization potential of the Ne*(2pi [J = 1]) atoms to the spin-orbit coupling and the electrostatic interaction between Ne* and He atoms leads to good agreement between theory and experiment.
Optimizing exoplanet transit searches around low-mass stars with inclination constraints

NASA Astrophysics Data System (ADS)

Herrero, E.; Ribas, I.; Jordi, C.; Guinan, E. F.; Engle, S. G.

2012-01-01

Aims: We investigate a method to increase the efficiency of a targeted exoplanet search with the transit technique by preselecting a subset of candidates from large catalogs of stars. Assuming spin-orbit alignment, this can be achieved by considering stars that have a higher probability to be oriented nearly equator-on (inclination close to 90°). Methods: We used activity-rotation velocity relations for low-mass stars with a convective envelope to study the dependence of the position in the activity-vsini diagram on the stellar axis inclination. We composed a catalog of G-, K-, M-type main-sequence simulated stars using isochrones, an isotropic inclination distribution and empirical relations to obtain their rotation periods and activity indexes. Then the activity-vsini diagram was completed and statistics were applied to trace the areas containing the higher ratio of stars with inclinations above 80°. A similar statistics was applied to stars from real catalogs with log(R'HK) and vsini data to find their probability of being oriented equator-on. Results: We present our method to generate the simulated star catalog and the subsequent statistics to find the highly inclined stars from real catalogs using the activity-vsini diagram. Several catalogs from the literature are analyzed and a subsample of stars with the highest probability of being equator-on is presented. Conclusions: Assuming spin-orbit alignment, the efficiency of an exoplanet transit search in the resulting subsample of probably highly inclined stars is estimated to be two to three times higher than with a general search without preselection. Table 4 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A147
Strong polarization-dependent terahertz modulation of aligned Ag nanowires on Si substrate.

PubMed

Lee, Gyuseok; Maeng, Inhee; Kang, Chul; Oh, Myoung-Kyu; Kee, Chul-Sik

2018-05-14

Optically tunable, strong polarization-dependent transmission of terahertz pulses through aligned Ag nanowires on a Si substrate is demonstrated. Terahertz pulses primarily pass through the Ag nanowires and the transmittance is weakly dependent on the angle between the direction of polarization of the terahertz pulse and the direction of nanowire alignment. However, the transmission of a terahertz pulse through optically excited materials strongly depends on the polarization direction. The extinction ratio increases as the power of the pumping laser increases. The enhanced polarization dependency is explained by the redistribution of photocarriers, which accelerates the sintering effect along the direction of alignment of the Ag nanowires. The photocarrier redistribution effect is examined by the enhancement of terahertz emission from the sample. Oblique metal nanowires on Si could be utilized for designing optically tunable terahertz polarization modulators.
The Electronic Behavior of Zinc-Finger Protein Binding Sites in the Context of the DNA Extended Ladder Model

NASA Astrophysics Data System (ADS)

Oiwa, Nestor; Cordeiro, Claudette; Heermann, Dieter

2016-05-01

Instead of ATCG letter alignments, typically used in bioinformatics, we propose a new alignment method using the probability distribution function of the bottom of the occupied molecular orbital (BOMO), highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO). We apply the technique to transcription factors with Cys2His2 zinc fingers. These transcription factors search for binding sites, probing for the electronic patterns at the minor and major DNA groves. The eukaryotic Cys2His2 zinc finger proteins bind to DNA ubiquitously at highly conserved domains. They are responsible for gene regulation and the spatial organization of DNA. To study and understand these zinc finger DNA-protein interactions, we use the extended ladder in the DNA model proposed by Zhu, Rasmussen, Balatsky & Bishop (2007) te{Zhu-2007}. Considering one single spinless electron in each nucleotide π-orbital along a double DNA chain (dDNA), we find a typical pattern for the bottom of BOMO, HOMO and LUMO along the binding sites. We specifically looked at two members of zinc finger protein family: specificity protein 1 (SP1) and early grown response 1 transcription factors (EGR1). When the valence band is filled, we find electrons in the purines along the nucleotide sequence, compatible with the electric charges of the binding amino acids in SP1 and EGR1 zinc finger.
Thrust vector control of upper stage with a gimbaled thruster during orbit transfer

NASA Astrophysics Data System (ADS)

Wang, Zhaohui; Jia, Yinghong; Jin, Lei; Duan, Jiajia

2016-10-01

In launching Multi-Satellite with One-Vehicle, the main thruster provided by the upper stage is mounted on a two-axis gimbal. During orbit transfer, the thrust vector of this gimbaled thruster (GT) should theoretically pass through the mass center of the upper stage and align with the command direction to provide orbit transfer impetus. However, it is hard to be implemented from the viewpoint of the engineering mission. The deviations of the thrust vector from the command direction would result in large velocity errors. Moreover, the deviations of the thrust vector from the upper stage mass center would produce large disturbance torques. This paper discusses the thrust vector control (TVC) of the upper stage during its orbit transfer. Firstly, the accurate nonlinear coupled kinematic and dynamic equations of the upper stage body, the two-axis gimbal and the GT are derived by taking the upper stage as a multi-body system. Then, a thrust vector control system consisting of the special attitude control of the upper stage and the gimbal rotation of the gimbaled thruster is proposed. The special attitude control defined by the desired attitude that draws the thrust vector to align with the command direction when the gimbal control makes the thrust vector passes through the upper stage mass center. Finally, the validity of the proposed method is verified through numerical simulations.
Suomi NPP VIIRS Prelaunch and On-orbit Geometric Calibration and Characterization

NASA Technical Reports Server (NTRS)

Wolfe, Robert E.; Lin, Guoqing; Nishihama, Masahiro; Tewari, Krishna P.; Tilton, James C.; Isaacman, Alice R.

2013-01-01

The Visible Infrared Imager Radiometer Suite (VIIRS) sensor was launched 28 October 2011 on the Suomi National Polarorbiting Partnership (SNPP) satellite. VIIRS has 22 spectral bands covering the spectrum between 0.412 m and 12.01 m, including 16 moderate resolution bands (M-bands) with a spatial resolution of 750 m at nadir, 5 imaging resolution bands (I-bands) with a spatial resolution of 375 m at nadir, and 1 day-night band (DNB) with a near-constant 750 m spatial resolution throughout the scan. These bands are located in a visible and near infrared (VisNIR) focal plane assembly (FPA), a short- and mid-wave infrared (SWMWIR) FPA and a long-wave infrared (LWIR) FPA. All bands, except the DNB, are co-registered for proper environmental data records (EDRs) retrievals. Observations from VIIRS instrument provide long-term measurements of biogeophysical variables for climate research and polar satellite data stream for the operational communitys use in weather forecasting and disaster relief and other applications. Well Earth-located (geolocated) instrument data is important to retrieving accurate biogeophysical variables. This paper describes prelaunch pointing and alignment measurements, and the two sets of on-orbit correction of geolocation errors, the first of which corrected error from 1,300 m to within 75 m (20 I-band pixel size), and the second of which fine tuned scan angle dependent errors, bringing VIIRS geolocation products to high maturity in one and a half years of the SNPP VIIRS on-orbit operations. Prelaunch calibration and the on-orbit characterization of sensor spatial impulse responses and band-to-band co-registration (BBR) are also described.
Fragment-orbital tunneling currents and electronic couplings for analysis of molecular charge-transfer systems.

PubMed

Hwang, Sang-Yeon; Kim, Jaewook; Kim, Woo Youn

2018-04-04

In theoretical charge-transfer research, calculation of the electronic coupling element is crucial for examining the degree of the electronic donor-acceptor interaction. The tunneling current (TC), representing the magnitudes and directions of electron flow, provides a way of evaluating electronic couplings, along with the ability of visualizing how electrons flow in systems. Here, we applied the TC theory to π-conjugated organic dimer systems, in the form of our fragment-orbital tunneling current (FOTC) method, which uses the frontier molecular-orbitals of system fragments as diabatic states. For a comprehensive test of FOTC, we assessed how reasonable the computed electronic couplings and the corresponding TC densities are for the hole- and electron-transfer databases HAB11 and HAB7. FOTC gave 12.5% mean relative unsigned error with regard to the high-level ab initio reference. The shown performance is comparable with that of fragment-orbital density functional theory, which gave the same error by 20.6% or 13.9% depending on the formulation. In the test of a set of nucleobase π stacks, we showed that the original TC expression is also applicable to nondegenerate cases under the condition that the overlap between the charge distributions of diabatic states is small enough to offset the energy difference. Lastly, we carried out visual analysis on the FOTC densities of thiophene dimers with different intermolecular alignments. The result depicts an intimate topological connection between the system geometry and electron flow. Our work provides quantitative and qualitative grounds for FOTC, showing it to be a versatile tool in characterization of molecular charge-transfer systems.
3D Modeling of Forbidden Line Emission in the Binary Wind Interaction Region of Eta Carinae

NASA Technical Reports Server (NTRS)

Madura, Thomas; Gull, T. R.; Owocki, S.; Okazaki, A. T.; Russell, C. M. P.

2010-01-01

We present recent work using three-dimensional (3D) Smoothed Particle Hydrodynamics (SPH) simulations to model the high ([Fe III], [Ar III], [Ne III] and [S III]) and low ([Fe II], [Ni II]) ionization forbidden emission lines observed in Eta Carinae using the HST/STIS. These structures are interpreted as the time-averaged, outer extensions of the primary wind and the wind-wind interaction region directly excited by the FUV of the hot companion star of this massive binary system. We discuss how analyzing the results of the 3D SPH simulations and synthetic slit spectra and comparing them to the spectra obtained with the HST/STIS helps us determine the absolute orientation of the binary orbit and helps remove the degeneracy inherent to models based solely on the observed RXTE X-ray light curve. A key point of this work is that spatially resolved observations like those with HST/STIS and comparison to 3D models are necessary to determine the alignment or misalignment of the orbital angular momentum axis with the Homunculus, or correspondingly, the alignment of the orbital plane with the Homunculus skirt.

Energizing the last phase of common-envelope removal

NASA Astrophysics Data System (ADS)

Soker, Noam

2017-11-01

We propose a scenario where a companion that is about to exit a common-envelope evolution (CEE) with a giant star accretes mass from the remaining envelope outside its deep orbit and launches jets that facilitate the removal of the remaining envelope. The jets that the accretion disc launches collide with the envelope and form hot bubbles that energize the envelope. Due to gravitational interaction with the envelope, which might reside in a circumbinary disc, the companion migrates farther in, but the inner boundary of the circumbinary disc continues to feed the accretion disc. While near the equatorial plane mass leaves the system at a very low velocity, along the polar directions velocities are very high. When the primary is an asymptotic giant branch star, this type of flow forms a bipolar nebula with very narrow waists. We compare this envelope-removal process with four other last-phase common-envelope-removal processes. We also note that the accreted gas from the envelope outside the orbit in the last phase of the CEE might carry with it angular momentum that is anti-aligned to the orbital angular momentum. We discuss the implications to the possibly anti-aligned spins of the merging black hole event GW170104.
Nonguiding Center Motion and Substorm Effects in the Magnetotail

NASA Technical Reports Server (NTRS)

Kaufmann, Richard L.; Kontodinas, Ioannis D.; Ball, Bryan M.; Larson, Douglas J.

1997-01-01

Thick and thin models of the middle magnetotail were developed using a consistent orbit tracing technique. It was found that currents carried near the equator by groups of ions with anisotropic distribution functions are not well approximated by the guiding center expressions. The guiding center equations fail primarily because the calculated pressure tensor is not magnetic field aligned. The pressure tensor becomes field aligned as one moves away from the equator, but here there is a small region in which the guiding center equations remain inadequate because the two perpendicular components of the pressure tensor are unequal. The significance of nonguiding center motion to substorm processes then was examined. One mechanism that may disrupt a thin cross-tail current sheet involves field changes that cause ions to begin following chaotic orbits. The lowest-altitude chaotic region, characterized by an adiabaticity parameter kappa approx. equal to 0.8, is especially important. The average cross-tail particle drift is slow, and we were unable to generate a thin current sheet using such ions. Therefore, any process that tends to create a thin current sheet in a region with kappa approaching 0.8 may cause the cross-tail current to get so low that it becomes insufficient to support the lobes. A different limit may be important in resonant orbit regions of a thin current sheet because particles reach a maximum cross-tail drift velocity. If the number of ions per unit length decreases as the tail is stretched, this part of the plasma sheet also may become unable to carry the cross-tail current needed to support the lobes. Thin sheets are needed for both resonant and chaotic orbit mechanisms because the distribution function must be highly structured. A description of current continuity is included to show how field aligned currents can evolve during the transition from a two-dimensional (2-D) to a 3-D configuration.
Improving Robotic Operator Performance Using Augmented Reality

NASA Technical Reports Server (NTRS)

Maida, James C.; Bowen, Charles K.; Pace, John W.

2007-01-01

The Special Purpose Dexterous Manipulator (SPDM) is a two-armed robot that functions as an extension to the end effector of the Space Station Robotics Manipulator System (SSRMS), currently in use on the International Space Station (ISS). Crew training for the SPDM is accomplished using a robotic hardware simulator, which performs most of SPDM functions under normal static Earth gravitational forces. Both the simulator and SPDM are controlled from a standard robotic workstation using a laptop for the user interface and three monitors for camera views. Most operations anticipated for the SPDM involve the manipulation, insertion, and removal of any of several types of Orbital Replaceable Unit (ORU), modules which control various ISS functions. Alignment tolerances for insertion of the ORU into its receptacle are 0.25 inch and 0.5 degree from nominal values. The pre-insertion alignment task must be performed within these tolerances by using available video camera views of the intrinsic features of the ORU and receptacle, without special registration markings. Since optimum camera views may not be available, and dynamic orbital lighting conditions may limit periods of viewing, a successful ORU insertion operation may require an extended period of time. This study explored the feasibility of using augmented reality (AR) to assist SPDM operations. Geometric graphical symbols were overlaid on one of the workstation monitors to afford cues to assist the operator in attaining adequate pre-insertion ORU alignment. Twelve skilled subjects performed eight ORU insertion tasks using the simulator with and without the AR symbols in a repeated measures experimental design. Results indicated that using the AR symbols reduced pre-insertion alignment error for all subjects and reduced the time to complete pre-insertion alignment for most subjects.
A molecular design principle of lyotropic liquid-crystalline conjugated polymers with directed alignment capability for plastic electronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Bong-Gi; Jeong, Eun Jeong; Chung, Jong Won

Conjugated polymers with a one-dimensional p-orbital overlap exhibit optoelectronic anisotropy. Their unique anisotropic properties can be fully realized in device applications only when the conjugated chains are aligned. Here, we report a molecular design principle of conjugated polymers to achieve concentration-regulated chain planarization, self-assembly, liquid-crystal-like good mobility and non-interdigitated side chains. As a consequence of these intra- and intermolecular attributes, chain alignment along an applied flow field occurs. This liquid-crystalline conjugated polymer was realized by incorporating intramolecular sulphur–fluorine interactions and bulky side chains linked to a tetrahedral carbon having a large form factor. By optimizing the polymer concentration and themore » flow field, we could achieve a high dichroic ratio of 16.67 in emission from conducting conjugated polymer films. Two-dimensional grazing-incidence X-ray diffraction was performed to analyse a well-defined conjugated polymer alignment. Thin-film transistors built on highly aligned conjugated polymer films showed more than three orders of magnitude faster carrier mobility along the conjugated polymer alignment direction than the perpendicular direction.« less
CO-ORBITING PLANES OF SUB-HALOS ARE SIMILARLY UNLIKELY AROUND PAIRED AND ISOLATED HOSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawlowski, Marcel S.; McGaugh, Stacy S., E-mail: marcel.pawlowski@case.edu

2014-07-01

Sub-halos in dark-matter-based cosmological simulations tend to be distributed approximately isotropically around their host. The existence of highly flattened, co-orbiting planes of satellite galaxies has therefore been identified as a possible problem for these cosmological models, but so far studies have not considered the hosts' environments. That satellite planes are now known around both major galaxies in the Local Group raises the question whether they are more likely to be found around paired hosts. In a first attempt to investigate this possibility, we focus on the flattening and orbital coherence of the 11 brightest satellite galaxies of the vast polarmore » structure (VPOS) around the Milky Way (MW). We search for VPOS analogs in the ''Exploring the Local Volume in Simulations'' suite of cosmological simulations, which consist of 24 paired and 24 isolated host halos. We do not find significant differences between the properties of sub-halo distributions around paired and isolated hosts. The observed flattening and the observed orbital alignment are each reproduced by only 0.2%-2% of paired and isolated systems incorporating the obscuration of satellites by randomly oriented galactic disks. Only 1 of all 4800 analyzed realizations (0.02%) reproduces both parameters simultaneously, but the average orbital pole of this sub-halo system does not align as well with the normal to the plane fit as observed. That the MW is part of a galaxy pair thus does not help to explain the existence of the VPOS if the satellite galaxies are identified with sub-halos found in dissipationless simulations.« less
Spin-Orbit Misalignments of Three Jovian Planets via Doppler Tomography

NASA Astrophysics Data System (ADS)

Johnson, Marshall C.; Cochran, William D.; Addison, Brett C.; Tinney, Chris G.; Wright, Duncan J.

2017-10-01

We present measurements of the spin-orbit misalignments of the hot Jupiters HAT-P-41 b and WASP-79 b, and the aligned warm Jupiter Kepler-448 b. We obtain these measurements with Doppler tomography, where we spectroscopically resolve the line profile perturbation during the transit due to the Rossiter-McLaughlin effect. We analyze time series spectra obtained during portions of five transits of HAT-P-41 b, and find a value of the spin-orbit misalignment of λ =-{22.1}-6.0{+0.8^\\circ }. We reanalyze the radial velocity Rossiter-McLaughlin data on WASP-79 b obtained by Addison et al. using Doppler tomographic methodology. We measure λ =-{99.1}-3.9{+4.1^\\circ }, consistent with but more precise than the value found by Addison et al. For Kepler-448 b we perform a joint fit to the Kepler light curve, Doppler tomographic data, and a radial velocity data set from Lillo-Box et al. We find an approximately aligned orbit (λ =-{7.1}-2.8{+4.2^\\circ }), in agreement with the value found by Bourrier et al. Through analysis of the Kepler light curve we measure a stellar rotation period of {P}{rot}=1.27+/- 0.11 days, and use this to argue that the full three-dimensional spin-orbit misalignment is small, \\psi ˜ 0^\\circ . Based in part on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.
Using Lunar Observations to Validate Pointing Accuracy and Geolocation, Detector Sensitivity Stability and Static Point Response of the CERES Instruments

NASA Technical Reports Server (NTRS)

Daniels, Janet L.; Smith, G. Louis; Priestley, Kory J.; Thomas, Susan

2014-01-01

Validation of in-orbit instrument performance is a function of stability in both instrument and calibration source. This paper describes a method using lunar observations scanning near full moon by the Clouds and Earth Radiant Energy System (CERES) instruments. The Moon offers an external source whose signal variance is predictable and non-degrading. From 2006 to present, these in-orbit observations have become standardized and compiled for the Flight Models -1 and -2 aboard the Terra satellite, for Flight Models-3 and -4 aboard the Aqua satellite, and beginning 2012, for Flight Model-5 aboard Suomi-NPP. Instrument performance measurements studied are detector sensitivity stability, pointing accuracy and static detector point response function. This validation method also shows trends per CERES data channel of 0.8% per decade or less for Flight Models 1-4. Using instrument gimbal data and computed lunar position, the pointing error of each detector telescope, the accuracy and consistency of the alignment between the detectors can be determined. The maximum pointing error was 0.2 Deg. in azimuth and 0.17 Deg. in elevation which corresponds to an error in geolocation near nadir of 2.09 km. With the exception of one detector, all instruments were found to have consistent detector alignment from 2006 to present. All alignment error was within 0.1o with most detector telescopes showing a consistent alignment offset of less than 0.02 Deg.
A fully relativistic twisted disc around a slowly rotating Kerr black hole: derivation of dynamical equations and the shape of stationary configurations

NASA Astrophysics Data System (ADS)

Zhuravlev, V. V.; Ivanov, P. B.

2011-08-01

In this paper we derive equations describing the dynamics and stationary configurations of a twisted fully relativistic thin accretion disc around a slowly rotating black hole. We assume that the inclination angle of the disc is small and that the standard relativistic generalization of the α model of accretion discs is valid when the disc is flat. We find that similar to the case of non-relativistic twisted discs the disc dynamics and stationary shapes can be determined by a pair of equations formulated for two complex variables describing the orientation of the disc rings and velocity perturbations induced by the twist. We analyse analytically and numerically the shapes of stationary twisted configurations of accretion discs having non-zero inclinations with respect to the black hole equatorial plane at large distances r from the black hole. It is shown that the stationary configurations depend on two parameters - the viscosity parameter α and the parameter ?, where δ* is the opening angle (δ*˜h/r, where h is the disc half-thickness and r is large) of a flat disc and a is the black hole rotational parameter. When a > 0 and ? the shapes depend drastically on the value of α. When α is small the disc inclination angle oscillates with radius with amplitude and radial frequency of the oscillations dramatically increasing towards the last stable orbit, Rms. When α has a moderately small value the oscillations do not take place but the disc does not align with the equatorial plane at small radii. The disc inclination angle either is increasing towards Rms or exhibits a non-monotonic dependence on the radial coordinate. Finally, when α is sufficiently large the disc aligns with the equatorial plane at small radii. When a < 0 the disc aligns with the equatorial plane for all values of α. The results reported here may have implications for determining the structure and variability of accretion discs close to Rms as well as for modelling of emission spectra coming from different sources, which are supposed to contain black holes.
Pairwise Sequence Alignment Library

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeff Daily, PNNL

2015-05-20

Vector extensions, such as SSE, have been part of the x86 CPU since the 1990s, with applications in graphics, signal processing, and scientific applications. Although many algorithms and applications can naturally benefit from automatic vectorization techniques, there are still many that are difficult to vectorize due to their dependence on irregular data structures, dense branch operations, or data dependencies. Sequence alignment, one of the most widely used operations in bioinformatics workflows, has a computational footprint that features complex data dependencies. The trend of widening vector registers adversely affects the state-of-the-art sequence alignment algorithm based on striped data layouts. Therefore, amore » novel SIMD implementation of a parallel scan-based sequence alignment algorithm that can better exploit wider SIMD units was implemented as part of the Parallel Sequence Alignment Library (parasail). Parasail features: Reference implementations of all known vectorized sequence alignment approaches. Implementations of Smith Waterman (SW), semi-global (SG), and Needleman Wunsch (NW) sequence alignment algorithms. Implementations across all modern CPU instruction sets including AVX2 and KNC. Language interfaces for C/C++ and Python.« less
Stability of Multi-Planet Systems in the Alpha Centauri System

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.

2017-01-01

We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales (Quarles & Lissauer 2016, Astron. J. 151, 111), as well as how closely-spaced planetary orbits can be within those regions in which individual planets can survive. Although individual planets on low inclination, low eccentricity, orbits can survive throughout the habitable zones of both stars, perturbations from the companion star imply that the spacing of planets in multi-planet systems within the habitable zones of each star must be significantly larger than the spacing of similar multi-planet systems orbiting single stars in order to be long-lived. Because the binary companion induces a forced eccentricity upon the orbits of planets in orbit around either star, appropriately-aligned circumstellar orbits with small initial eccentricities are stable to slightly larger initial semimajor axes than are initially circular orbits. Initial eccentricities close to forced eccentricities can have a much larger affect on how closely planetary orbits can be spaced, and therefore on how many planets may remain in the habitable zones, although the required spacing remains significantly higher than for planets orbiting single stars.
On non-coplanar Hohmann transfer using angles as parameters

NASA Astrophysics Data System (ADS)

Rincón, Ángel; Rojo, Patricio; Lacruz, Elvis; Abellán, Gabriel; Díaz, Sttiwuer

2015-09-01

We study a more complex case of Hohmann orbital transfer of a satellite by considering non-coplanar and elliptical orbits, instead of planar and circular orbits. We use as parameter the angle between the initial and transference planes that minimizes the energy, and therefore the fuel of a satellite, through the application of two non-tangential impulses for all possible cases. We found an analytical expression that minimizes the energy for each configuration. Some reasonable physical constraints are used: we apply impulses at perigee or apogee of the orbit, we consider the duration of the impulse to be short compared to the duration of the trip, we take the nodal line of three orbits to be coincident and the three semimajor axes to lie in the same plane. We study the only four possible cases but assuming non-coplanar elliptic orbits. In addition, we validate our method through a numerical solution obtained by using some of the actual orbital elements of Sputnik I and Vanguard I satellites. For these orbits, we found that the most fuel-efficient transfer is obtained by applying the initial impulse at apocenter and keeping the transfer orbit aligned with the initial orbit.
Space shuttle navigation analysis

NASA Technical Reports Server (NTRS)

Jones, H. L.; Luders, G.; Matchett, G. A.; Sciabarrasi, J. E.

1976-01-01

A detailed analysis of space shuttle navigation for each of the major mission phases is presented. A covariance analysis program for prelaunch IMU calibration and alignment for the orbital flight tests (OFT) is described, and a partial error budget is presented. The ascent, orbital operations and deorbit maneuver study considered GPS-aided inertial navigation in the Phase III GPS (1984+) time frame. The entry and landing study evaluated navigation performance for the OFT baseline system. Detailed error budgets and sensitivity analyses are provided for both the ascent and entry studies.
Europa and Callisto under the Watchful Gaze of Jupiter

NASA Image and Video Library

2000-12-21

One moment in an ancient, orbital dance is caught in this color picture taken by NASA Cassini spacecraft on Dec. 7, 2000, just as two of Jupiter four major moons, Europa and Callisto, were nearly perfectly aligned with each other.
Spin injection into Pt-polymers with large spin-orbit coupling

NASA Astrophysics Data System (ADS)

Sun, Dali; McLaughlin, Ryan; Siegel, Gene; Tiwari, Ashutosh; Vardeny, Z. Valy

2014-03-01

Organic spintronics has entered a new era of devices that integrate organic light-emitting diodes (OLED) in organic spin valve (OSV) geometry (dubbed bipolar organic spin valve, or spin-OLED), for actively manipulating the device electroluminescence via the spin alignment of two ferromagnetic electrodes (Science 337, 204-209, 2012; Appl. Phys. Lett. 103, 042411, 2013). Organic semiconductors that contain heavy metal elements have been widely used as phosphorescent dopants in white-OLEDs. However such active materials are detrimental for OSV operation due to their large spin-orbit coupling (SOC) that may limit the spin diffusion length and thus spin-OLED based on organics with large SOC is a challenge. We report the successful fabrication of OSVs based on pi-conjugated polymers which contain intrachain Platinum atoms (dubbed Pt-polymers). Spin injection into the Pt-polymers is investigated by the giant magnetoresistance (GMR) effect as a function of bias voltage, temperature and polymer layer thickness. From the GMR bias voltage dependence we infer that the ``impendence mismatch'' between ferromagnetic electrodes and Pt-polymer may be suppressed due to the large SOC. Research sponsored by the NSF (Grant No. DMR-1104495) and NSF-MRSEC (DMR 1121252) at the University of Utah.
Providing relay communications support for the Mars Environmental Survey (MESUR) mission

NASA Technical Reports Server (NTRS)

Swenson, Byron L.; Friedlander, Alan L.

1992-01-01

The purpose of the Mars Environmental Survey (MESUR) mission is to put in place, over several launch opportunities, a constellation of Mars landers to make long-term surface observations of the circulation of the atmosphere and changes in climate, and to record the seismic activity of the planetary crust. Short-term objectives will also be addressed. An orbital communications infrastructure capable of providing regular high-rate data transfer to earth from the landers, which are scattered globally from pole to pole, is key to accomplishing the mission goals. A study is thereby presented of the orbit selection for the orbiter spacecraft, which will provide this support, and the relay communications operation. It is concluded that adequate communications support for the objectives of the MESUR mission can be provided by a single orbiter, provided care is taken in the selection of the size and orientation (i.e., inclination and apse line alignment) of the spacecraft orbit.
Hydrostar Thermal and Structural Deformation Analyses of Antenna Array Concept

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.; Hope, Drew J.

1998-01-01

The proposed Hydrostar mission used a large orbiting antenna array to demonstrate synthetic aperture technology in space while obtaining global soil moisture data. In order to produce accurate data, the array was required to remain as close as possible to its perfectly aligned placement while undergoing the mechanical and thermal stresses induced by orbital changes. Thermal and structural analyses for a design concept of this antenna array were performed. The thermal analysis included orbital radiation calculations, as well as parametric studies of orbit altitude, material properties and coating types. The thermal results included predicted thermal distributions over the array for several cases. The structural analysis provided thermally-driven deflections based on these cases, as well as based on a 1-g inertial load. In order to minimize the deflections of the array in orbit, the use of XN70, a carbon-reinforced polycyanate composite, was recommended.
High Fidelity Modeling of SRP and Its Effect on the Relative Motion of Starshade and WFIRST

NASA Technical Reports Server (NTRS)

Farres, Ariadna; Webster, Cassandra; Folta, Dave

2018-01-01

In this paper we perform a detailed analysis of how Solar Radiation Pressure (SRP) affects the relative motion of two spacecrafts, the Wide-Field Infrared Survey Telescope (WFIRST) and Starshade, orbiting in the vicinity of the Sun-Earth L2. While WFIRST orbits about its own Libration Point Orbit (LPO), Starshade will fly a specific trajectory to align with WFIRST and observe a Design Reference Mission of pre-determined target stars. In this analysis, we focus on the transfer orbit for Starshade from one observation to the other. We will describe how SRP affects the dynamics of the Starshade relative to WFIRSTand how relevant this effect is in order to get an accurate estimate of the total difference in velocity (delta v).
Galactic cosmic ray gradients, field-aligned and latitudinal, among Voyagers 1/2 and IMP-8

NASA Technical Reports Server (NTRS)

Roelof, E. C.; Decker, R. B.; Krimigis, S. M.; Venkatesan, D.; Lazarus, A. J.

1982-01-01

The present investigation represents a summary of a comprehensive analysis of the same subject conducted by Roelof et al. (1981). It is pointed out that the tandem earth-Jupiter trajectories of the Voyager 1/2 spacecraft, combined with baseline measurements from the earth-orbiting IMP 7/8 spacecraft, provide the first opportunity for unambiguously separating latitude from radial or field-aligned effects in galactic cosmic ray gradients. Attention is given to the method of data analysis, and the separation of field-aligned and latitudinal gradients. It is found that latitudinal gradients approximately equal to or greater than 1 percent per deg in the cosmic ray intensity were a common feature of the interplanetary medium between 1 and 5 AU in 1977-78. Except in the most disturbed periods, cosmic ray intensities are well-ordered in field-aligned structures.
Measuring Parameters of Massive Black Hole Binaries with Partially-Aligned Spins

NASA Technical Reports Server (NTRS)

Lang, Ryan N.; Hughes, Scott A.; Cornish, Neil J.

2010-01-01

It is important to understand how well the gravitational-wave observatory LISA can measure parameters of massive black hole binaries. It has been shown that including spin precession in the waveform breaks degeneracies and produces smaller expected parameter errors than a simpler, precession-free analysis. However, recent work has shown that gas in binaries can partially align the spins with the orbital angular momentum, thus reducing the precession effect. We show how this degrades the earlier results, producing more pessimistic errors in gaseous mergers. However, we then add higher harmonics to the signal model; these also break degeneracies, but they are not affected by the presence of gas. The harmonics often restore the errors in partially-aligned binaries to the same as, or better than/ those that are obtained for fully precessing binaries with no harmonics. Finally, we investigate what LISA measurements of spin alignment can tell us about the nature of gas around a binary,
Energy-level alignment at organic heterointerfaces

PubMed Central

Oehzelt, Martin; Akaike, Kouki; Koch, Norbert; Heimel, Georg

2015-01-01

Today’s champion organic (opto-)electronic devices comprise an ever-increasing number of different organic-semiconductor layers. The functionality of these complex heterostructures largely derives from the relative alignment of the frontier molecular-orbital energies in each layer with respect to those in all others. Despite the technological relevance of the energy-level alignment at organic heterointerfaces, and despite continued scientific interest, a reliable model that can quantitatively predict the full range of phenomena observed at such interfaces is notably absent. We identify the limitations of previous attempts to formulate such a model and highlight inconsistencies in the interpretation of the experimental data they were based on. We then develop a theoretical framework, which we demonstrate to accurately reproduce experiment. Applying this theory, a comprehensive overview of all possible energy-level alignment scenarios that can be encountered at organic heterojunctions is finally given. These results will help focus future efforts on developing functional organic interfaces for superior device performance. PMID:26702447

Alignment between Satellite and Central Galaxies in the SDSS DR7: Dependence on Large-scale Environment

NASA Astrophysics Data System (ADS)

Wang, Peng; Luo, Yu; Kang, Xi; Libeskind, Noam I.; Wang, Lei; Zhang, Youcai; Tempel, Elmo; Guo, Quan

2018-06-01

The alignment between satellites and central galaxies has been studied in detail both in observational and theoretical works. The widely accepted fact is that satellites preferentially reside along the major axis of their central galaxy. However, the origin and large-scale environmental dependence of this alignment are still unknown. In an attempt to determine these variables, we use data constructed from Sloan Digital Sky Survey DR7 to investigate the large-scale environmental dependence of this alignment with emphasis on examining the alignment’s dependence on the color of the central galaxy. We find a very strong large-scale environmental dependence of the satellite–central alignment (SCA) in groups with blue centrals. Satellites of blue centrals in knots are preferentially located perpendicular to the major axes of the centrals, and the alignment angle decreases with environment, namely, when going from knots to voids. The alignment angle strongly depends on the {}0.1(g-r) color of centrals. We suggest that the SCA is the result of a competition between satellite accretion within large-scale structure (LSS) and galaxy evolution inside host halos. For groups containing red central galaxies, the SCA is mainly determined by the evolution effect, while for blue central dominated groups, the effect of the LSS plays a more important role, especially in knots. Our results provide an explanation for how the SCA forms within different large-scale environments. The perpendicular case in groups and knots with blue centrals may also provide insight into understanding similar polar arrangements, such as the formation of the Milky Way and Centaurus A’s satellite system.
A Hybrid Kinetic Model of Asymmetric Thin Current Sheets with Sheared Flows in a Collisionless Plasma

DTIC Science & Technology

2010-12-27

z are aligned with those of the usual Geocentric Sun - Earth (aSE) coordinates. In this frame, +x points from the Earth to the Sun , +y points out of...current sheet (box) in the solar wind. x, y, and z are aligned with the aSE coordinates, with +X pointing from the Earth toward the Sun , +y out of the...account the exact ion orbits and such properties as the anisotropic and nondiagonal pressure tensor and sheared ion flows. Figure 1a shows a schematic
Cellular Reflectarray Antenna

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

2010-01-01

The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.
Torsional stress impedance and magneto-impedance in (Co0.95Fe0.05)72.5 Si12.5B15 amorphous wire with helical induced anisotropy

NASA Astrophysics Data System (ADS)

Blanco, J. M.; Zhukov, A. P.; González, J.

1999-12-01

The magneto-impedance effect icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/ZH = [Z(H)-Z(Hmax)]/Z(Hmax) has been measured in (Fe0.95Co0.05)72.5B15Si12.5 wire under torsion stress, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> (torsion angle per unit length) with axial magnetic field (H) as parameter. Without stress (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)H(H) dependence has a non-monotonous shape with first an increase of total impedance Z and then a decrease, i.e. shows a maximum at certain axial magnetic field Hm. It was found that the torsion stress dependence of electrical impedance (torsion impedance), (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> = [Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>)-Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max)]/Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max), has asymmetric character with a clear maximum at torsion angle, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> around 7icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 in as-cast wire, while (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> reaches a maximum around 170%. Thermal treatments under torsion stress (without and with a previous annealing stage) develop a helical anisotropy on the amorphous wire, which drastically modifies the (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> response. Such treatments were carried out by using current annealing which resulted in a drastic increase of the maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> up to 225%, and a change of torsion dependence of icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z with a tendency to a finally symmetric dependence of (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/>(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>). The maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> ratio, (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> m, was obtained under torsion stress of icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> = 20icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 (in a torsion annealed sample) and = 11 rad m-1 (with pre-annealing and torsion annealing). Observed dependences were explained taking into account the frozen-in magneto-elastic anisotropy owing to the internal stress distribution during the fabrication process, the helical anisotropies induced by the torsion strain and that developed by thermal treatment under torsion stress (torsion annealing). The differences in the shape and intensity of the maximum ( Z/Z) m between the torsion annealed and pre-annealed and torsion annealed samples should be ascribed to the visco-elastic character of the helical anisotropy induced by torsion stress.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Hellier, Coel; Anderson, D. R.; Smalley, B.

WASP-19b has the shortest orbital period of any known exoplanet, orbiting at only 1.2 times the Roche tidal radius. By observing the Rossiter-McLaughlin effect we show that WASP-19b's orbit is aligned, with {lambda} = 4.{sup 0}6 {+-} 5.{sup 0}2. Using, in addition, a spectroscopic vsin I and the observed rotation period we conclude that the obliquity, {psi}, is less than 20{sup 0}. Further, the eccentricity of the orbit is less than 0.02. We argue that hot Jupiters with orbital periods as short as that of WASP-19b are two orders of magnitude less common than hot Jupiters at the 3-4 daymore » 'pileup'. We discuss the evolution of WASP-19b's orbit and argue that most likely it was first moved to near twice the Roche limit by third-body interactions, and has since spiralled inward to its current location under tidal decay. This is compatible with a stellar tidal-dissipation quality factor, Q'{sub *}, of order 10{sup 7}.« less
Angular dependence of spin-orbit spin-transfer torques

NASA Astrophysics Data System (ADS)

Lee, Ki-Seung; Go, Dongwook; Manchon, Aurélien; Haney, Paul M.; Stiles, M. D.; Lee, Hyun-Woo; Lee, Kyung-Jin

2015-04-01

In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.
Gate-tunable resonant tunneling in double bilayer graphene heterostructures.

PubMed

Fallahazad, Babak; Lee, Kayoung; Kang, Sangwoo; Xue, Jiamin; Larentis, Stefano; Corbet, Christopher; Kim, Kyounghwan; Movva, Hema C P; Taniguchi, Takashi; Watanabe, Kenji; Register, Leonard F; Banerjee, Sanjay K; Tutuc, Emanuel

2015-01-14

We demonstrate gate-tunable resonant tunneling and negative differential resistance in the interlayer current-voltage characteristics of rotationally aligned double bilayer graphene heterostructures separated by hexagonal boron nitride (hBN) dielectric. An analysis of the heterostructure band alignment using individual layer densities, along with experimentally determined layer chemical potentials indicates that the resonance occurs when the energy bands of the two bilayer graphene are aligned. We discuss the tunneling resistance dependence on the interlayer hBN thickness, as well as the resonance width dependence on mobility and rotational alignment.
Alignment Test Results of the JWST Pathfinder Telescope Mirrors in the Cryogenic Environment

NASA Technical Reports Server (NTRS)

Whitman, Tony L.; Wells, Conrad; Hadaway, James; Knight, J. Scott; Lunt, Sharon

2016-01-01

After integration of the Optical Telescope Element (OTE) to the Integrated Science Instrument Module (ISIM) to become the OTIS, the James Webb Space Telescope OTIS is tested at NASAs Johnson Space Center (JSC) in the cryogenic vacuum Chamber A for alignment and optical performance. The alignment of the mirrors comprises a sequence of steps as follows: The mirrors are coarsely aligned using photogrammetry cameras with reflective targets attached to the sides of the mirrors. Then a multi-wavelength interferometer is aligned to the 18-segment primary mirror using cameras at the center of curvature to align reflected light from the segments and using fiducials at the edge of the primary mirror. Once the interferometer is aligned, the 18 primary mirror segments are then adjusted to optimize wavefront error of the aggregate mirror. This process phases the piston and tilt positions of all the mirror segments. An optical fiber placed at the Cassegrain focus of the telescope then emits light towards the secondary mirror to create a collimated beam emitting from the primary mirror. Portions of the collimated beam are retro-reflected from flat mirrors at the top of the chamber to pass through the telescope to the SI detector. The image on the detector is used for fine alignment of the secondary mirror and a check of the primary mirror alignment using many of the same analysis techniques used in the on-orbit alignment. The entire process was practiced and evaluated in 2015 at cryogenic temperature with the Pathfinder telescope.
The Time Evolution of Eta Carinae's Colliding Winds

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Madura, T. I.; Grobe, J. H.; Corcoran, M. F.

2011-01-01

We report new HST/STIS observations that map the high-ionization forbidden line emission in the inner arc second of Eta Car, the first that fully image the extended wind-wind interaction region of the massive colliding wind binary. These observations were obtained after the 2009.0 periastron at orbital phases 0.084, 0.163, and 0.323 of the 5.54-year spectroscopic cycle. We analyze the variations in brightness and morphology of the emission, and find that blue-shifted emission (-400 to -200 km/s is symmetric and elongated along the northeast-southwest axis, while the red-shifted emission (+ 100 to +200 km/s) is asymmetric and extends to the north-northwest. Comparison to synthetic images generated from a 3-D dynamical model strengthens the 3-D orbital orientation found by Madura et al. (2011), with an inclination i = 138 deg, argument of periapsis w = 270 deg, and an orbital axis that is aligned at the same P A on the sky as the symmetry axis of the Homunculus, 312 deg. We discuss the potential that these and future mappings have for constraining the stellar parameters of the companion star and the long-term variability of the system. Plain-Language Abstract: With HST, we resolved the interacting winds of the binary, Eta Carinae. With a 3-D model, we find the binary orbit axis is aligned to the Homunculus axis. This suggests a connection between the binary and Homunculus ejection mechanism.
Bottom boundary layer spectral dissipation estimates in the presence of wave motions

NASA Astrophysics Data System (ADS)

Gross, T. F.; Williams, A. J.; Terray, E. A.

1994-08-01

Turbulence measurements are an essential element of the Sediment TRansport Events on Shelves and Slopes experiment (STRESS). Sediment transport under waves is initiated within the wave boundary layer at the seabed, at most a few tens of centimeters deep. The suspended load is carried by turbulent diffusion above the wave boundary layer. Quantification of the turbulent diffusion active above the wave boundary layer requires estimates of shear stress or energy dissipation in the presence of oscillating flows. Measurements by Benthic Acoustic Stress Sensors of velocity fluctuations were used to derive the dissipation rate from the energy level of the spectral inertial range (the -5/3 spectrum). When the wave orbital velocity is of similar magnitude to the mean flow, kinematic effects on the estimation techniques of stress and dissipation must be included. Throughout the STRESS experiment there was always significant wave energy affecting the turbulent bottom boundary layer. LUMLEY and TERRAY [(1983) Journal of Physical Oceanography, 13, 2000-2007] presented a theory describing the effect of orbital motions on kinetic energy spectra. Their model is used here with observations of spectra taken within a turbulent boundary layer which is affected by wave motion. While their method was an explicit solution for circular wave orbits aligned with mean current we extrapolated it to the case of near bed horizontal motions, not aligned with the current. The necessity of accounting for wave orbital motion is demonstrated, but variability within the field setting limited our certainty of the improvement in accuracy the corrections afforded.
ON THE TIDAL ORIGIN OF HOT JUPITER STELLAR OBLIQUITY TRENDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, Rebekah I., E-mail: rdawson@berkeley.edu

It is debated whether the two hot Jupiter populations—those on orbits misaligned from their host star's spin axis and those well-aligned—result from two migration channels or from two tidal realignment regimes. Here I demonstrate that equilibrium tides raised by a planet on its star can account for three observed spin-orbit alignment trends: the aligned orbits of hot Jupiters orbiting cool stars, the planetary mass cut-off for retrograde planets, and the stratification by planet mass of cool host stars' rotation frequencies. The first trend can be caused by strong versus weak magnetic braking (the Kraft break), rather than realignment of themore » star's convective envelope versus the entire star. The second trend can result from a small effective stellar moment of inertia participating in the tidal realignment in hot stars, enabling massive retrograde planets to partially realign to become prograde. The third trend is attributable to higher-mass planets more effectively counteracting braking to spin up their stars. Both hot and cool stars require a small effective stellar moment of inertia participating in the tidal realignment, e.g., an outer layer weakly coupled to the interior. I demonstrate via Monte Carlo that this model can match the observed trends and distributions of sky-projected misalignments and stellar rotation frequencies. I discuss implications for inferring hot Jupiter migration mechanisms from obliquities, emphasizing that even hot stars do not constitute a pristine sample.« less
Implications of the Low Binary Black Hole Aligned Spins Observed by LIGO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hotokezaka, Kenta; Piran, Tsvi

We explore the implications of the low-spin components along the orbital axis observed in an Advanced LIGO O1 run on binary black hole (BBH) merger scenarios in which the merging BBHs have evolved from field binaries. The coalescence time determines the initial orbital separation of BBHs. This, in turn, determines whether the stars are synchronized before collapse, and hence determines their projected spins. Short coalescence times imply synchronization and large spins. Among known stellar objects, Wolf–Rayet (WR) stars seem to be the only progenitors consistent with the low aligned spins observed in LIGO’s O1, provided that the orbital axis maintainsmore » its direction during the collapse. We calculate the spin distribution of BBH mergers in the local universe, and its redshift evolution for WR progenitors. Assuming that the BBH formation rate peaks around a redshift of ∼2–3, we show that BBH mergers in the local universe are dominated by low-spin events. The high-spin population starts to dominate at a redshift of ∼0.5–1.5. WR stars are also progenitors of long gamma-ray bursts that take place at a comparable rate to BBH mergers. We discuss the possible connection between the two phenomena. Additionally, we show that hypothetical Population III star progenitors are also possible. Although WR and Population III progenitors are consistent with the current data, both models predict a non-vanishing fraction of high positive values of the BBHs’ aligned spin. If those are not detected within the coming LIGO/Virgo runs, it will be unlikely that the observed BBHs formed via field binaries.« less
The Nuclear Spectroscopic Telescope Array (NuSTAR)

NASA Technical Reports Server (NTRS)

Harrison, Fiona A.; Boggs, Steven; Christensen, Finn; Craig, William; Hailey, Charles; Stern, Daniel; Zhang, William; Angelini, Lorella; An, Hong Jun; Bhalereo, Varun;

2010-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (5 - 80 keV) telescope to orbit. NuSTAR will offer a factor 50 - 100 sensitivity improvement compared to previous collimated or coded mask imagers that have operated in this energy band. In addition, NuSTAR provides sub-arcminute imaging with good spectral resolution over a 12-arcminute field of view. After launch, NuSTAR will carry out a two-year primary science mission that focuses on four key programs: studying the evolution of massive black holes through surveys carried out in fields with excellent multiwavelength coverage, understanding the population of compact objects and the nature of the massive black hole in the center of the Milky Way, constraining explosion dynamics and nucleosynthesis in supernovae, and probing the nature of particle acceleration in relativistic jets in active galactic nuclei. A number of additional observations will be included in the primary mission, and a. guest observer program will be proposed for an extended mission to expand the range of scientific targets. The payload consists of two co-aligned depth-graded multilayer coated grazing incidence optics focused onto solid state CdZnTe pixel detectors. To be launched in early 2012 on a Pegasus rocket into a low-inclination Earth orbit. NuSTAR largely avoids SAA passages, and will therefore have low and stable detector backgrounds. The telescope achieves a 10.15-meter focal length through on-orbit deployment of all mast. An aspect and alignment metrology system enable reconstruction of the absolute aspect and variations in the telescope alignment resulting from mast flexure during ground data processing. Data will be publicly available at GSFC's High Energy Astrophysics Science Archive Research Center (HEASARC) following validation at the science operations center located at Caltech.

An independent determination of Fomalhaut b's orbit and the dynamical effects on the outer dust belt

NASA Astrophysics Data System (ADS)

Beust, H.; Augereau, J.-C.; Bonsor, A.; Graham, J. R.; Kalas, P.; Lebreton, J.; Lagrange, A.-M.; Ertel, S.; Faramaz, V.; Thébault, P.

2014-01-01

Context. The nearby star Fomalhaut harbors a cold, moderately eccentric (e ~ 0.1) dust belt with a sharp inner edge near 133 au. A low-mass, common proper motion companion, Fomalhaut b (Fom b), was discovered near the inner edge and was identified as a planet candidate that could account for the belt morphology. However, the most recent orbit determination based on four epochs of astrometry over eight years reveals a highly eccentric orbit (e = 0.8 ± 0.1) that appears to cross the belt in the sky plane projection. Aims: We perform here a full orbital determination based on the available astrometric data to independently validate the orbit estimates previously presented. Adopting our values for the orbital elements and their associated uncertainties, we then study the dynamical interaction between the planet and the dust ring, to check whether the proposed disk sculpting scenario by Fom b is plausible. Methods: We used a dedicated MCMC code to derive the statistical distributions of the orbital elements of Fom b. Then we used symplectic N-body integration to investigate the dynamics of the dust belt, as perturbed by a single planet. Different attempts were made assuming different masses for Fom b. We also performed a semi-analytical study to explain our results. Results: Our results are in good agreement with others regarding the orbit of Fom b. We find that the orbit is highly eccentric, is close to apsidally aligned with the belt, and has a mutual inclination relative to the belt plane of <29° (67% confidence). If coplanar, this orbit crosses the disk. Our dynamical study then reveals that the observed planet could sculpt a transient belt configuration with a similar eccentricity to what is observed, but it would not be simultaneously apsidally aligned with the planet. This transient configuration only occurs a short time after the planet is placed on such an orbit (assuming an initially circular disk), a time that is inversely proportional to the planet's mass, and that is in any case much less than the 440 Myr age of the star. Conclusions: We constrain how long the observed dust belt could have survived with Fom b on its current orbit, as a function of its possible mass. This analysis leads us to conclude that Fom b is likely to have low mass, that it is unlikely to be responsible for the sculpting of the belt, and that it supports the hypothesis of a more massive, less eccentric planet companion Fomalhaut c.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Winn, Joshua N.; Albrecht, Simon; Johnson, John Asher

We present new radial velocity (RV) measurements of HAT-P-13, a star with two previously known companions: a transiting giant planet 'b' with an orbital period of 3 days and a more massive object 'c' on a 1.2 yr, highly eccentric orbit. For this system, dynamical considerations would lead to constraints on planet b's interior structure, if it could be shown that the orbits are coplanar and apsidally locked. By modeling the Rossiter-McLaughlin effect, we show that planet b's orbital angular momentum vector and the stellar spin vector are well aligned on the sky ({lambda} = 1.9 {+-} 8.6 deg). Themore » refined orbital solution favors a slightly eccentric orbit for planet b (e = 0.0133 {+-} 0.0041), although it is not clear whether it is apsidally locked with c's orbit ({Delta}{omega} = 36{sup +27}{sub -36} deg). We find a long-term trend in the star's RV and interpret it as evidence for an additional body 'd', which may be another planet or a low-mass star. Predictions are given for the next few inferior conjunctions of c, when transits may happen.« less
Spin-Orbit Misalignment of Two-Planet-System KOI-89 Via Gravity Darkening

NASA Astrophysics Data System (ADS)

Ahlers, Jonathon; Barnes, Jason W.; Barnes, Rory

2015-12-01

We investigate the potential causes of spin-orbit misalignment in multiplanetary systems via two-planet-system KOI-89. We focus on this system because it can experimentally constrain the outstanding hypotheses that have been proposed to cause misalignments. Using gravity darkening, we constrain both the spin-orbit angles and the angle between the planes of the orbits. Our best-fit model shows that the 85-day-orbit and 208-day-orbit planets are misaligned from the host star's rotation axis by 72° ± 3° and 73° (+11 -5°), respectively. From these results, we limit KOI-89's potential causes of spin-orbit misalignment based on three criteria: agreement with KOI-89's fundamental parameters, the capability to cause extreme misalignment, and conformance with mutually aligned planets. Our results disfavor planet-embryo collisions, chaotic evolution of stellar spin, magnetic torquing, coplanar high-eccentricity migration, and inclination resonance, limiting possible causes to star-disk binary interactions, disk warping via planet-disk interactions, Kozai resonance, planet-planet scattering, or internal gravity waves in the convective interior of the star.
Transiting circumbinary planets Kepler-34 b and Kepler-35 b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welsh, William F.; Orosz, Jerome A.; Carter, Joshua A.

Most Sun-like stars in the Galaxy reside in gravitationally-bound pairs of stars called 'binary stars'. While long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of Kepler-16. Incontrovertible evidence was provided by the miniature eclipses ('transits') of the stars by the planet. However, questions remain about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we present two additional transiting circumbinary planets, Kepler-34 and Kepler-35. Each is a low-density gas giant planet on an orbit closely aligned with that of its parentmore » stars. Kepler-34 orbits two Sun-like stars every 289 days, while Kepler-35 orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. Due to the orbital motion of the stars, the planets experience large multi-periodic variations in incident stellar radiation. The observed rate of circumbinary planets implies > ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.« less
DETERMINATION OF THE INTERIOR STRUCTURE OF TRANSITING PLANETS IN MULTIPLE-PLANET SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batygin, Konstantin; Bodenheimer, Peter; Laughlin, Gregory, E-mail: kbatygin@gps.caltech.ed

Tidal dissipation within a short-period transiting extrasolar planet perturbed by a companion object can drive orbital evolution of the system to a so-called tidal fixed point, in which the apses of the transiting planet and its perturber are aligned, and variations in orbital eccentricities vanish. Significant contribution to the apsidal precession rate is made by gravitational quadrupole fields, created by the transiting planets tidal and rotational distortions. The fixed-point orbital eccentricity of the inner planet is therefore a strong function of its interior structure. We illustrate these ideas in the specific context of the recently discovered HAT-P-13 exoplanetary system, andmore » show that one can already glean important insights into the physical properties of the inner transiting planet. We present structural models of the planet, which indicate that its observed radius can be maintained for a one-parameter sequence of models that properly vary core mass and tidal energy dissipation in the interior. We use an octupole-order secular theory of the orbital dynamics to derive the dependence of the inner planet's eccentricity, e{sub b} , on its tidal Love number, k {sub 2b}. We find that the currently measured eccentricity, e{sub b} = 0.021 +- 0.009, implies 0.116 < k {sub 2b} < 0.425, 0 M {sub +} < M {sub core} < 120 M {sub +}, and 10, 000 < Q{sub b} < 300, 000. Improved measurement of the eccentricity will soon allow for far tighter limits to be placed on all of these quantities, and will provide an unprecedented probe into the interior structure of an extrasolar planet.« less
Co-registration of Laser Altimeter Tracks with Digital Terrain Models and Applications in Planetary Science

NASA Technical Reports Server (NTRS)

Glaeser, P.; Haase, I.; Oberst, J.; Neumann, G. A.

2013-01-01

We have derived algorithms and techniques to precisely co-register laser altimeter profiles with gridded Digital Terrain Models (DTMs), typically derived from stereo images. The algorithm consists of an initial grid search followed by a least-squares matching and yields the translation parameters at sub-pixel level needed to align the DTM and the laser profiles in 3D space. This software tool was primarily developed and tested for co-registration of laser profiles from the Lunar Orbiter Laser Altimeter (LOLA) with DTMs derived from the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) stereo images. Data sets can be co-registered with positional accuracy between 0.13 m and several meters depending on the pixel resolution and amount of laser shots, where rough surfaces typically result in more accurate co-registrations. Residual heights of the data sets are as small as 0.18 m. The software can be used to identify instrument misalignment, orbit errors, pointing jitter, or problems associated with reference frames being used. Also, assessments of DTM effective resolutions can be obtained. From the correct position between the two data sets, comparisons of surface morphology and roughness can be made at laser footprint- or DTM pixel-level. The precise co-registration allows us to carry out joint analysis of the data sets and ultimately to derive merged high-quality data products. Examples of matching other planetary data sets, like LOLA with LRO Wide Angle Camera (WAC) DTMs or Mars Orbiter Laser Altimeter (MOLA) with stereo models from the High Resolution Stereo Camera (HRSC) as well as Mercury Laser Altimeter (MLA) with Mercury Dual Imaging System (MDIS) are shown to demonstrate the broad science applications of the software tool.
Effects of biaxial oscillatory shear stress on endothelial cell proliferation and morphology.

PubMed

Chakraborty, Amlan; Chakraborty, Sutirtha; Jala, Venkatakrishna R; Haribabu, Bodduluri; Sharp, M Keith; Berson, R Eric

2012-03-01

Wall shear stress (WSS) on anchored cells affects their responses, including cell proliferation and morphology. In this study, the effects of the directionality of pulsatile WSS on endothelial cell proliferation and morphology were investigated for cells grown in a Petri dish orbiting on a shaker platform. Time and location dependent WSS was determined by computational fluid dynamics (CFD). At low orbital speed (50 rpm), WSS was shown to be uniform (0-1 dyne/cm(2)) across the bottom of the dish, while at higher orbital speed (100 and 150 rpm), WSS remained fairly uniform near the center and fluctuated significantly (0-9 dyne/cm(2)) near the side walls of the dish. Since WSS on the bottom of the dish is two-dimensional, a new directional oscillatory shear index (DOSI) was developed to quantify the directionality of oscillating shear. DOSI approached zero for biaxial oscillatory shear of equal magnitudes near the center and approached one for uniaxial pulsatile shear near the wall, where large tangential WSS dominated a much smaller radial component. Near the center (low DOSI), more, smaller and less elongated cells grew, whereas larger cells with greater elongation were observed in the more uniaxial oscillatory shear (high DOSI) near the periphery of the dish. Further, cells aligned with the direction of the largest component of shear but were randomly oriented in low magnitude biaxial shear. Statistical analyses of the individual and interacting effects of multiple factors (DOSI, shear magnitudes and orbital speeds) showed that DOSI significantly affected all the responses, indicating that directionality is an important determinant of cellular responses. Copyright © 2011 Wiley Periodicals, Inc.

Ferromagnetism induced by entangled charge and orbital orderings in ferroelectric titanate perovskites

PubMed Central

Bristowe, N. C.; Varignon, J.; Fontaine, D.; Bousquet, E.; Ghosez, Ph.

2015-01-01

In magnetic materials, the Pauli exclusion principle typically drives anti-alignment between electron spins on neighbouring species resulting in antiferromagnetic behaviour. Ferromagnetism exhibiting spontaneous spin alignment is a fairly rare behaviour, but once materialized is often associated with itinerant electrons in metals. Here we predict and rationalize robust ferromagnetism in an insulating oxide perovskite structure based on the popular titanate series. In half-doped layered titanates, the combination of Jahn–Teller and oxygen breathing motions opens a band gap and creates an unusual charge and orbital ordering of the Ti d electrons. It is argued that this intriguingly intricate electronic network favours the elusive inter-site ferromagnetic (FM) ordering, on the basis of intra-site Hund's rules. Finally, we find that the layered oxides are also ferroelectric with a spontaneous polarization approaching that of BaTiO3. The concepts are general and design principles of the technologically desirable FM ferroelectric multiferroics are presented. PMID:25807180
Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal

PubMed Central

Frietsch, B.; Bowlan, J.; Carley, R.; Teichmann, M.; Wienholdt, S.; Hinzke, D.; Nowak, U.; Carva, K.; Oppeneer, P. M.; Weinelt, M.

2015-01-01

The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale. PMID:26355196
Radiometric and geometric assessment of data from the RapidEye constellation of satellites

USGS Publications Warehouse

Chander, Gyanesh; Haque, Md. Obaidul; Sampath, Aparajithan; Brunn, A.; Trosset, G.; Hoffmann, D.; Roloff, S.; Thiele, M.; Anderson, C.

2013-01-01

To monitor land surface processes over a wide range of temporal and spatial scales, it is critical to have coordinated observations of the Earth's surface using imagery acquired from multiple spaceborne imaging sensors. The RapidEye (RE) satellite constellation acquires high-resolution satellite images covering the entire globe within a very short period of time by sensors identical in construction and cross-calibrated to each other. To evaluate the RE high-resolution Multi-spectral Imager (MSI) sensor capabilities, a cross-comparison between the RE constellation of sensors was performed first using image statistics based on large common areas observed over pseudo-invariant calibration sites (PICS) by the sensors and, second, by comparing the on-orbit radiometric calibration temporal trending over a large number of calibration sites. For any spectral band, the individual responses measured by the five satellites of the RE constellation were found to differ <2–3% from the average constellation response depending on the method used for evaluation. Geometric assessment was also performed to study the positional accuracy and relative band-to-band (B2B) alignment of the image data sets. The position accuracy was assessed by comparing the RE imagery against high-resolution aerial imagery, while the B2B characterization was performed by registering each band against every other band to ensure that the proper band alignment is provided for an image product. The B2B results indicate that the internal alignments of these five RE bands are in agreement, with bands typically registered to within 0.25 pixels of each other or better.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Fabrycky, Daniel C.; Winn, Joshua N.

One possible diagnostic of planet formation, orbital migration, and tidal evolution is the angle {psi} between a planet's orbital axis and the spin axis of its parent star. In general, {psi} cannot be measured, but for transiting planets one can measure the angle {lambda} between the sky projections of the two axes via the Rossiter-McLaughlin effect. Here, we show how to combine measurements of {lambda} in different systems to derive statistical constraints on {psi}. We apply the method to 11 published measurements of {lambda}, using two different single-parameter distributions to describe the ensemble. First, assuming a Rayleigh distribution (or moremore » precisely, a Fisher distribution on a sphere), we find that the peak value is less than 22{sup 0} with 95% confidence. Second, assuming that a fraction f of the orbits have random orientations relative to the stars, and the remaining fraction (1 - f) are perfectly aligned, we find f < 0.36 with 95% confidence. This latter model fits the data better than the Rayleigh distribution, mainly because the XO-3 system was found to be strongly misaligned while the other 10 systems are consistent with perfect alignment. If the XO-3 result proves robust, then our results may be interpreted as evidence for two distinct modes of planet migration.« less
Band alignment of 2D WS2/HfO2 interfaces from x-ray photoelectron spectroscopy and first-principles calculations

NASA Astrophysics Data System (ADS)

Zhu, H. L.; Zhou, C. J.; Tang, B. S.; Yang, W. F.; Chai, J. W.; Tay, W. L.; Gong, H.; Pan, J. S.; Zou, W. D.; Wang, S. J.; Chi, D. Z.

2018-04-01

We report on the growth of two-dimensional (2D) WS2 on high-k HfO2/Si substrates by reactive sputtering deposition. Raman, x-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy characterizations indicate that the 2D WS2 layers exhibit high-quality crystallinity and exact stoichiometry. Through high-resolution XPS valence spectra, we find a type I alignment at the interface of monolayer WS2/HfO2 with a valence band offset (VBO) of 1.95 eV and a conduction band offset (CBO) of 1.57 eV. The VBO and CBO are also found to increase up to 2.24 eV and 2.09 eV, respectively, with increasing WS2 layers. This is consistent with the results obtained from our first-principles calculations. Our theoretical calculations reveal that the remarkable splitting and shift of the W 5 d z 2 orbital originating from interlayer orbital coupling in thicker WS2 films induce a reduction of its bandgap, leading to an increase in both the VBO and CBO. This observation can be attributed to the asymmetric splitting at different high symmetric k-points caused by the interlayer orbital coupling.
THE WELL-ALIGNED ORBIT OF WASP-84b: EVIDENCE FOR DISK MIGRATION OF A HOT JUPITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, D. R.; Triaud, A. H. M. J.; Turner, O. D.

We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69M{sub Jup} planet in an 8.52 day orbit around a G9V/K0V star, to be λ = −0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration.more » Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first “hot Jupiter” (P<10 d) to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (T{sub eff} < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.« less
Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

PubMed Central

Wang, Xu; Le, Anh-Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

2016-01-01

We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method. PMID:27025410
Reverse Kinematic Analysis and Uncertainty Analysis of the Space Shuttle AFT Propulsion System (APS) POD Lifting Fixture

NASA Technical Reports Server (NTRS)

Brink, Jeffrey S.

2005-01-01

The space shuttle Aft Propulsion System (APS) pod requires precision alignment to be installed onto the orbiter deck. The Ground Support Equipment (GSE) used to perform this task cannot be manipulated along a single Cartesian axis without causing motion along the other Cartesian axes. As a result, manipulations required to achieve a desired motion are not intuitive. My study calculated the joint angles required to align the APS pod, using reverse kinematic analysis techniques. Knowledge of these joint angles will allow the ground support team to align the APS pod more safely and efficiently. An uncertainty analysis was also performed to estimate the accuracy associated with this approach and to determine whether any inexpensive modifications can be made to further improve accuracy.
Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

NASA Astrophysics Data System (ADS)

Wang, Xu; Le, Anh-Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

2016-03-01

We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.
Design, Qualification, and On Orbit Performance of the CALIPSO Aerosol Lidar Transmitter

NASA Technical Reports Server (NTRS)

Hovis, Floyd E.; Witt, Greg; Sullivan, Edward T.; Le, Khoa; Weimer, Carl; Applegate, Jeff; Luck, William S., Jr.; Verhapen, Ron; Cisewski, Michael S.

2007-01-01

The laser transmitter for the CALIPSO aerosol lidar mission has been operating on orbit as planned since June 2006. This document discusses the optical and laser system design and qualification process that led to this success. Space-qualifiable laser design guidelines included the use of mature laser technologies, the use of alignment sensitive resonator designs, the development and practice of stringent contamination control procedures, the operation of all optical components at appropriately derated levels, and the proper budgeting for the space-qualification of the electronics and software.
Ultracold collisions between spin-orbit-coupled dipoles: General formalism and universality

NASA Astrophysics Data System (ADS)

Wang, Jia; Hougaard, Christiaan R.; Mulkerin, Brendan C.; Liu, Xia-Ji

2018-04-01

A theoretical study of the low-energy scattering properties of two aligned identical bosonic and fermionic dipoles in the presence of isotropic spin-orbit coupling is presented. A general treatment of particles with arbitrary (pseudo)spin is given in the framework of multichannel scattering. At ultracold temperatures and away from shape resonances or closed-channel dominated resonances, the cross section can be well described within the Born approximation to within corrections due to the s -wave scattering. We compare our findings with numerical calculations and find excellent agreement.
Six-State Quantum Key Distribution Using Photons with Orbital Angular Momentum

NASA Astrophysics Data System (ADS)

Li, Jun-Lin; Wang, Chuan

2010-11-01

A new implementation of high-dimensional quantum key distribution (QKD) protocol is discussed. Using three mutual unbiased bases, we present a d-level six-state QKD protocol that exploits the orbital angular momentum with the spatial mode of the light beam. The protocol shows that the feature of a high capacity since keys are encoded using photon modes in d-level Hilbert space. The devices for state preparation and measurement are also discussed. This protocol has high security and the alignment of shared reference frames is not needed between sender and receiver.
Optimized effective potential in real time: Problems and prospects in time-dependent density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mundt, Michael; Kuemmel, Stephan

2006-08-15

The integral equation for the time-dependent optimized effective potential (TDOEP) in time-dependent density-functional theory is transformed into a set of partial-differential equations. These equations only involve occupied Kohn-Sham orbitals and orbital shifts resulting from the difference between the exchange-correlation potential and the orbital-dependent potential. Due to the success of an analog scheme in the static case, a scheme that propagates orbitals and orbital shifts in real time is a natural candidate for an exact solution of the TDOEP equation. We investigate the numerical stability of such a scheme. An approximation beyond the Krieger-Li-Iafrate approximation for the time-dependent exchange-correlation potential ismore » analyzed.« less
Angular dependence of coercivity derived from alignment dependence of coercivity in Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Matsuura, Yutaka; Nakamura, Tetsuya; Sumitani, Kazushi; Kajiwara, Kentaro; Tamura, Ryuji; Osamura, Kozo

2018-01-01

Experimental results of the alignment dependence of the coercivity in Nd-Fe-B sintered magnets showed that the angle of magnetization reversal for anisotropically aligned magnets was bigger than that obtained from the theoretical results calculated using the postulation that every grain independently reverses its magnetization direction following the 1/cos θ law. The angles of reversed magnetization (θ1) for Nd13.48Co0.55B5.76Febal. with alignment α=0.95 and for Nd12.75Dy0.84B5.81Co0.55Febal. with α=0.96 were 30° and 36°, respectively, which were very similar to that of an ideal magnet with a Gaussian distribution (σ=31° and 44°, respectively) of the grain alignment. In this model, we postulated that every grain independently reversed according to the 1/cos θ law. The calculation results for the angular dependence of the coercivity using the values θ1=ω1(0°)=30°, σ=31° and θ1=ω1(0°)=36°, σ=44° could qualitatively and convincingly explain the observed angular dependence of the coercivity of Nd14.2B6.2Co1.0Febal. and Nd14.2Dy0.3B6.2Co1.0Febal.. It is speculated that the magnetic domain wall is pinned at grains tilted away from the easy magnetization direction, and when the magnetic domain wall de-pins from the tilted grains, the magnetic domain wall jumps through several grains. We suggest that the coercive force of the aligned magnet behaves like a low-aligned magnet owing to the magnetization reversal of the crust of the grains induced by the pinning and subsequent jumping of the magnetic domain wall.
Ionosphere-magnetosphere coupling

NASA Technical Reports Server (NTRS)

Kaufmann, Richard L.

1994-01-01

Principal results are presented for the four papers that were supported from this grant. These papers include: 'Mapping and Energization in the Magnetotail. 1. Magnetospheric Boundaries; 'Mapping and Energization in the Magnetotail. 2. Particle Acceleration'; 'Cross-Tail Current: Resonant Orbits'; and 'Cross-Tail Current, Field-Aligned Current, and B(sub y)'.
Alignment test results of the JWST Pathfinder Telescope mirrors in the cryogenic environment

NASA Astrophysics Data System (ADS)

Whitman, Tony L.; Wells, Conrad; Hadaway, James B.; Knight, J. Scott; Lunt, Sharon

2016-07-01

After integration of the Optical Telescope Element (OTE) to the Integrated Science Instrument Module (ISIM) to become the OTIS, the James Webb Space Telescope OTIS is tested at NASA's Johnson Space Center (JSC) in the cryogenic vacuum Chamber A for alignment and optical performance. The alignment of the mirrors comprises a sequence of steps as follows: The mirrors are coarsely aligned using photogrammetry cameras with reflective targets attached to the sides of the mirrors. Then a multi-wavelength interferometer is aligned to the 18-segment primary mirror using cameras at the center of curvature to align reflected light from the segments and using fiducials at the edge of the primary mirror. Once the interferometer is aligned, the 18 primary mirror segments are then adjusted to optimize wavefront error of the aggregate mirror. This process phases the piston and tilt positions of all the mirror segments. An optical fiber placed at the Cassegrain focus of the telescope then emits light towards the secondary mirror to create a collimated beam emitting from the primary mirror. Portions of the collimated beam are retro-reflected from flat mirrors at the top of the chamber to pass through the telescope to the Science Instrument (SI) detector. The image on the detector is used for fine alignment of the secondary mirror and a check of the primary mirror alignment using many of the same analysis techniques used in the on-orbit alignment. The entire process was practiced and evaluated in 2015 at cryogenic temperature with the Pathfinder telescope.
An ultra stable optical bench for the magnetic survey satellite

NASA Technical Reports Server (NTRS)

Wingate, C. A., Jr.; Coughlin, T. B.; Sullivan, R. M.

1978-01-01

The Magsat optical bench has been designed and built to hold the alignment of five optical elements to deflections of 1-2 arcsec during orbital operation. The bench has been designed to withstand alignment changes during the launch and prestabilization phases of the mission. Severe weight constraints, in conjunction with the thermal and structural requirements, led to the choice of graphite-fiber-reinforced epoxy egg crate core and face sheets for the bench construction. Active temperature control was necessary to meet thermal deflection objectives, and novel kinematic mountings were required to prevent spacecraft bending from deflecting the bench.
Alignment methods: strategies, challenges, benchmarking, and comparative overview.

PubMed

Löytynoja, Ari

2012-01-01

Comparative evolutionary analyses of molecular sequences are solely based on the identities and differences detected between homologous characters. Errors in this homology statement, that is errors in the alignment of the sequences, are likely to lead to errors in the downstream analyses. Sequence alignment and phylogenetic inference are tightly connected and many popular alignment programs use the phylogeny to divide the alignment problem into smaller tasks. They then neglect the phylogenetic tree, however, and produce alignments that are not evolutionarily meaningful. The use of phylogeny-aware methods reduces the error but the resulting alignments, with evolutionarily correct representation of homology, can challenge the existing practices and methods for viewing and visualising the sequences. The inter-dependency of alignment and phylogeny can be resolved by joint estimation of the two; methods based on statistical models allow for inferring the alignment parameters from the data and correctly take into account the uncertainty of the solution but remain computationally challenging. Widely used alignment methods are based on heuristic algorithms and unlikely to find globally optimal solutions. The whole concept of one correct alignment for the sequences is questionable, however, as there typically exist vast numbers of alternative, roughly equally good alignments that should also be considered. This uncertainty is hidden by many popular alignment programs and is rarely correctly taken into account in the downstream analyses. The quest for finding and improving the alignment solution is complicated by the lack of suitable measures of alignment goodness. The difficulty of comparing alternative solutions also affects benchmarks of alignment methods and the results strongly depend on the measure used. As the effects of alignment error cannot be predicted, comparing the alignments' performance in downstream analyses is recommended.
Gravity Recovery and Interior Laboratory (GRAIL) Mission: Status at the Initiation of the Science Mapping Phase

NASA Technical Reports Server (NTRS)

Zuber, Maria T.; Smith, David E.; Asmar, Sami W.; Alomon; Konopliv, Alexander S.; Lemoine, Frank G.; Melosh, H. Jay; Neumann, Gregory A.; Phillips. Roger J.; Solomon, Sean C.;

2012-01-01

The Gravity Recovery And Interior Laboratory (GRAIL) mission, a component of NASA's Discovery Program, launched successfully from Cape Canaveral Air Force Station on September 10, 2011. The dual spacecraft traversed independent, low-energy trajectories to the Moon via the EL-1 Lagrange point and inserted into elliptical, 11.5-hour polar orbits around the Moon on December 31, 2011, and January 1, 2012. The spacecraft are currently executing a series of maneuvers to circularize their orbits at 55-km mean altitude. Once the mapping orbit is achieved, the spacecraft will undergo additional maneuvers to align them into mapping configuration. The mission is on track to initiate the Science Phase on March 8, 2012.

Japanese MAGSAT Team

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator)

1982-01-01

CHRONINT and investigator B tapes as well as CHRONFIN data are being analyzed using a graphical display to illustrate X.Y,Z components as well as their residuals from the MGST (4/81) model. In addition to surveys of the vicinity of Japan, an aerial magnetic survey was conducted around Syowa Station in the Antarctic. Relative data collected by polar orbiting satellites are also being studied. Techniques used to separate external and internal fields from the vector data along the orbital paths; analysis of the frequency of the toroidal current in the equatorial ionosphere; investigation of the sudden storm commencement observed by MAGSAT; determination of the structure of field aligned currents associated with substorms; and calculation of the total electric current passing through the plane encircled by the MAGSAT orbit are discussed.

Dynamic behavior of solar wind as revealed by a correlation study of magnetic fields observed at the Venus and Earth orbits

NASA Technical Reports Server (NTRS)

Marubashi, K.

1995-01-01

Correlations between interplanetary magnetic fields (IMFs) at 0.72 AU and 1.0 AU have been examined using data sets obtained from the Pioneer Venus orbiter and Earth-orbiting spacecraft. While the two-sector structures are evident in long-term variations at these two heliocentric distances, the corresponding auto-correlation coefficients are consistently smaller at 1.0 AU than at 0.72 AU. This suggests that the IMF structures become less persistent at 1.0 AU due to the effects of changing solar wind dynamics between the Venus and Earth orbits. Short-term variations exhibit generally poor correlations between IMFs near Venus and those near Earth, though good correlations are sometimes obtained for well-defined structures when the Sun, Venus, and Earth are closely aligned. The rather poor correlations in the background streams indicate that the IMFs are still changing between the Venus and Earth orbits under the strong influence of solar wind dynamics.
Orbital loop currents in iron-based superconductors

NASA Astrophysics Data System (ADS)

Klug, Markus; Kang, Jian; Fernandes, Rafael M.; Schmalian, Jörg

2018-04-01

We show that the antiferromagnetic state commonly observed in the phase diagrams of the iron-based superconductors necessarily triggers loop currents characterized by charge transfer between different Fe 3 d orbitals. This effect is rooted on the glide-plane symmetry of these materials and on the existence of an atomic spin-orbit coupling that couples states at the X and Y points of the 1-Fe Brillouin zone. In the particular case in which the magnetic moments are aligned parallel to the magnetic ordering vector direction, which is the moment configuration most commonly found in the iron-based superconductors, these loop currents involve the dx y orbital and either the dy z orbital (if the moments point along the y axis) or the dx z orbitals (if the moments point along the x axis). We show that the two main manifestations of the orbital loop currents are the emergence of magnetic moments in the pnictide/chalcogen site and an orbital-selective band splitting in the magnetically ordered state, both of which could be detected experimentally. Our results highlight the unique intertwining between orbital and spin degrees of freedom in the iron-based superconductors, and reveal the emergence of an unusual correlated phase that may impact the normal state and superconducting properties of these materials.
Chandra X-Ray Observatory Pointing Control System Performance During Transfer Orbit and Initial On-Orbit Operations

NASA Technical Reports Server (NTRS)

Quast, Peter; Tung, Frank; West, Mark; Wider, John

2000-01-01

The Chandra X-ray Observatory (CXO, formerly AXAF) is the third of the four NASA great observatories. It was launched from Kennedy Space Flight Center on 23 July 1999 aboard the Space Shuttle Columbia and was successfully inserted in a 330 x 72,000 km orbit by the Inertial Upper Stage (IUS). Through a series of five Integral Propulsion System burns, CXO was placed in a 10,000 x 139,000 km orbit. After initial on-orbit checkout, Chandra's first light images were unveiled to the public on 26 August, 1999. The CXO Pointing Control and Aspect Determination (PCAD) subsystem is designed to perform attitude control and determination functions in support of transfer orbit operations and on-orbit science mission. After a brief description of the PCAD subsystem, the paper highlights the PCAD activities during the transfer orbit and initial on-orbit operations. These activities include: CXO/IUS separation, attitude and gyro bias estimation with earth sensor and sun sensor, attitude control and disturbance torque estimation for delta-v burns, momentum build-up due to gravity gradient and solar pressure, momentum unloading with thrusters, attitude initialization with star measurements, gyro alignment calibration, maneuvering and transition to normal pointing, and PCAD pointing and stability performance.
Angular dependence of coercivity in isotropically aligned Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Matsuura, Yutaka; Nakamura, Tetsuya; Sumitani, Kazushi; Kajiwara, Kentaro; Tamura, Ryuji; Osamura, Kozo

2018-05-01

In order to understand the coercivity mechanism in Nd-Fe-B sintered magnets, the angular dependence of the coercivity of an isotropically aligned Nd15Co1.0B6Febal. sintered magnet was investigated through magnetization measurements using a vibrating sample magnetometer. These results are compared with the angular dependence calculated under the assumption that the magnetization reversal of each grain follows the Kondorskii law or, in other words, the 1/cos θ law for isotropic alignment distributions. The calculated angular dependence of the coercivity agrees very well with the experiment for magnetic fields applied between angles of 0 and 60°, and it is expected that the magnetization reversal occurs in each grain individually followed the 1/cos θ law. In contrast, this agreement between calculation and experiment is not found for anisotropic Nd-Fe-B samples. This implies that the coercivity of the aligned magnets depends upon the de-pinning of the domain walls from pinning sites. When the de-pinning occurs, it is expected that the domain walls are displaced through several grains at once.
Simulation and analyses of the aeroassist flight experiment attitude update method

NASA Technical Reports Server (NTRS)

Carpenter, J. R.

1991-01-01

A method which will be used to update the alignment of the Aeroassist Flight Experiment's Inertial Measuring Unit is simulated and analyzed. This method, the Star Line Maneuver, uses measurements from the Space Shuttle Orbiter star trackers along with an extended Kalman filter to estimate a correction to the attitude quaternion maintained by an Inertial Measuring Unit in the Orbiter's payload bay. This quaternion is corrupted by on-orbit bending of the Orbiter payload bay with respect to the Orbiter navigation base, which is incorporated into the payload quaternion when it is initialized via a direct transfer of the Orbiter attitude state. The method of updating this quaternion is examined through verification of baseline cases and Monte Carlo analysis using a simplified simulation, The simulation uses nominal state dynamics and measurement models from the Kalman filter as its real world models, and is programmed on Microvax minicomputer using Matlab, and interactive matrix analysis tool. Results are presented which confirm and augment previous performance studies, thereby enhancing confidence in the Star Line Maneuver design methodology.
Effective Induction Heating around Strongly Magnetized Stars

NASA Astrophysics Data System (ADS)

Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.; Noack, L.; Lüftinger, T.; Zaitsev, V. V.; Lammer, H.

2018-05-01

Planets that are embedded in the changing magnetic fields of their host stars can experience significant induction heating in their interiors caused by the planet’s orbital motion. For induction heating to be substantial, the planetary orbit has to be inclined with respect to the stellar rotation and dipole axes. Using WX UMa, for which the rotation and magnetic axes are aligned, as an example, we show that for close-in planets on inclined orbits, induction heating can be stronger than the tidal heating occurring inside Jupiter’s satellite Io; namely, it can generate a surface heat flux exceeding 2 W m‑2. An internal heating source of such magnitude can lead to extreme volcanic activity on the planet’s surface, possibly also to internal local magma oceans, and to the formation of a plasma torus around the star aligned with the planetary orbit. A strongly volcanically active planet would eject into space mostly SO2, which would then dissociate into oxygen and sulphur atoms. Young planets would also eject CO2. Oxygen would therefore be the major component of the torus. If the O I column density of the torus exceeds ≈1012 cm‑2, the torus could be revealed by detecting absorption signatures at the position of the strong far-ultraviolet O I triplet at about 1304 Å. We estimate that this condition is satisfied if the O I atoms in the torus escape the system at a velocity smaller than 1–10 km s‑1. These estimates are valid also for a tidally heated planet.
Generalized Roche potential for misaligned binary systems - Properties of the critical lobe

NASA Technical Reports Server (NTRS)

Avni, Y.; Schiller, N.

1982-01-01

The paper considers the Roche potential for binary systems where the stellar rotation axis is not aligned with the orbital revolution axis. It is shown that, as the degree of misalignment varies, internal Lagrangian points and external Lagrangian points may switch their roles. A systematic method to identify the internal Lagrangian point and to calculate the volume of the critical lobe is developed, and numerical results for a wide range of parameters of binary systems with circular orbits are presented. For binary systems with large enough misalignment, discrete changes occur in the topological structure of the equipotential surfaces as the orbital phase varies. The volume of the critical lobe has minima, as a function of orbital phase, at the two instances when the secondary crosses the equatorial plane of the primary. In semidetached systems, mass transfer may be confined to the vicinity of these two instances.
Cornering and wear behavior of the Space Shuttle Orbiter main gear tire

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.

1987-01-01

One of the factors needed to describe the handling characteristics of the Space Shuttle Orbiter during the landing rollout is the response of the vehicle's tires to variations in load and yaw angle. An experimental investigation of the cornering characteristics of the Orbiter main gear tires was conducted at the NASA Langley Research Center Aircraft Landing Dynamics Facility. This investigation compliments earlier work done to define the Orbiter nose tire cornering characteristics. In the investigation, the effects of load and yaw angle were evaluated by measuring parameters such as side load and drag load, and obtaining measurements of aligning torque. Because the tire must operate on an extremely rough runway at the Shuttle Landing Facility at Kennedy Space Center (KSC), tests were also conducted to describe the wear behavior of the tire under various conditions on a simulated KSC runway surface. Mathematical models for both the cornering and the wear behavior are discussed.
The synchronous orbit magnetic field data set

NASA Technical Reports Server (NTRS)

Mcpherron, R. L.

1979-01-01

The magnetic field at synchronous orbit is the result of superposition of fields from many sources such as the earth, the magnetopause, the geomagnetic tail, the ring current and field-aligned currents. In addition, seasonal changes in the orientation of the earth's dipole axis causes significant changes in each of the external sources. Main reasons for which the synchronous orbit magnetic field data set is a potentially valuable resource are outlined. The primary reason why synchronous magnetic field data have not been used more extensively in magnetic field modeling is the presence of absolute errors in the measured fields. Nevertheless, there exists a reasonably large collection of synchronous orbit magnetic field data. Some of these data can be useful in quantitative modeling of the earth's magnetic field. A brief description is given of the spacecraft, the magnetometers, the standard graphical data displays, and the digital data files.
Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion.

PubMed

Zhou, Yixuan; E, Yiwen; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

2016-12-14

Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.
Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

NASA Astrophysics Data System (ADS)

Zhou, Yixuan; Yiwen, E.; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

2016-12-01

Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.
Advanced understanding on electronic structure of molecular semiconductors and their interfaces

NASA Astrophysics Data System (ADS)

Akaike, Kouki

2018-03-01

Understanding the electronic structure of organic semiconductors and their interfaces is critical to optimizing functionalities for electronics applications, by rational chemical design and appropriate combination of device constituents. The unique electronic structure of a molecular solid is characterized as (i) anisotropic electrostatic fields that originate from molecular quadrupoles, (ii) interfacial energy-level lineup governed by simple electrostatics, and (iii) weak intermolecular interactions that make not only structural order but also energy distributions of the frontier orbitals sensitive to atmosphere and interface growth. This article shows an overview on these features with reference to the improved understanding of the orientation-dependent electronic structure, comprehensive mechanisms of molecular doping, and energy-level alignment. Furthermore, the engineering of ionization energy by the control of the electrostatic fields and work function of practical electrodes by contact-induced doping is briefly described for the purpose of highlighting how the electronic structure impacts the performance of organic devices.
Search for gravitational waves from binary black hole inspiral, merger, and ringdown in LIGO-Virgo data from 2009-2010

NASA Astrophysics Data System (ADS)

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Ast, S.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Bao, Y.; Barayoga, J. C. B.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Beck, D.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bhadbade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bond, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Charlton, P.; Chassande-Mottin, E.; Chen, W.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Dent, T.; Dergachev, V.; DeRosa, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Paolo Emilio, M.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorsher, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Endrőczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Farr, B. F.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M. A.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gáspár, M. E.; Gelencser, G.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; James, E.; Jang, Y. J.; Jaranowski, P.; Jesse, E.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Keitel, D.; Kelley, D.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, H.; Kim, K.; Kim, N.; Kim, Y. M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Lam, P. K.; Landry, M.; Langley, A.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Lhuillier, V.; Li, J.; Li, T. G. F.; Lindquist, P. E.; Litvine, V.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Logue, J.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Morriss, S. R.; Mosca, S.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Necula, V.; Nelson, J.; Neri, I.; Newton, G.; Nguyen, T.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Oldenberg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Penn, S.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pihlaja, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Poux, C.; Prato, M.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, M.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J. G.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Vahlbruch, H.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2013-01-01

We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20,20)M⊙ coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for nonspinning components, and also evaluate the dependence of the search sensitivity on component spins aligned with the orbital angular momentum. We find an upper limit at 90% confidence on the coalescence rate of BBH with nonspinning components of mass between 19 and 28M⊙ of 3.3×10-7 mergers Mpc-3yr-1.
Stereochemical Alignment in Triphospha[3]ferrocenophanes

PubMed Central

Borucki, Stefan; Kelemen, Zsolt; Maurer, Martin; Bruhn, Clemens

2017-01-01

Abstract A series of triphospha[3]ferrocenophanes of the type Fe(C5H4‐PtBu)2PX with X=H, F, Cl, Br, I, NEt2, tBu has been prepared and characterized by heteronuclear NMR spectroscopy and X‐ray crystallography. Despite having three stereogenic centers, the selective formation of a reduced number of diastereomers (either one or two) has been observed for these ferrocenophanes. Theoretical calculations revealed that the inversion of the central stereogenic center inverts the frontier orbital sequence leading to either an iron or a phosphorus centered HOMO depending on the respective diastereomer. CV measurements supported these results. For the all‐tert‐butyl substituted [3]ferrocenophane Fe(C5H4)2(PtBu)3 a chiral staggered conformation has been found in the solid state which differs substantially from the only other all‐organo substituted [3]ferrocenophane, Fe(C5H4)2(PPh)3. PMID:28557205
Control of magnetism in dilute magnetic semiconductor (Ga,Mn)As films by surface decoration of molecules

NASA Astrophysics Data System (ADS)

Wang, Hailong; Wang, Xiaolei; Xiong, Peng; Zhao, Jianhua

2016-03-01

The responses of magnetic moments to external stimuli such as magnetic-field, heat, light and electric-field have been utilized to manipulate the magnetism in magnetic semiconductors, with many of the novel ideas applied even to ferromagnetic metals. Here, we review a new experimental development on the control of magnetism in (Ga,Mn)As thin films by surface decoration of organic molecules: Molecules deposited on the surface of (Ga,Mn)As thin films are shown to be capable of significantly modulating their saturation magnetization and Curie temperature. These phenomena are shown to originate from the carrier-mediated ferromagnetism in (Ga,Mn)As and the surface molecules acting as acceptors or donors depending on their highest occupied molecular orbitals, resembling the charge transfer mechanism in a pn junction in which the equilibrium state is reached on the alignment of Fermi levels.
Flexible Electrostatic Technology for Capture and Handling Project

NASA Technical Reports Server (NTRS)

Keys, Andrew; Bryan, Tom; Horwitz, Chris; Rakoczy, John; Waggoner, Jason

2015-01-01

To NASA unfunded & planned missions: This new capability to sense proximity, flexibly align to, and attractively grip and capture practically any object in space without any pre-designed physical features or added sensors or actuators will enable or enhance many of MSFC's strategic emphasis areas in space transportation, and space systems such as: 1. A Flexible Electrostatic gripper can enable the capture, gripping and releasing of an extraterrestrial sample of different minerals or a sample canister (metallic or composite) without requiring a handle or grapple fixture.(B) 2. Flexible self-aligning in-space capture/soft docking or berthing of ISS resupply vehicles, pressurized modules, or nodes for in-space assembly and shielding, radiator, and solar Array deployment for space habitats (C) 3. The flexible electrostatic gripper when combined with a simple steerable extendible boom can grip, position, and release objects of various shapes and materials with low mass and power without any prior handles or physical accommodations or surface contamination for ISS experiment experiments and in-situ repair.(F)(G) 4. The Dexterous Docking concept previously proposed to allow simple commercial resupply ships to station-keep and capture either ISS or an Exploration vehicle for supply or fluid transfer lacked a self-sensing, compliant, soft capture gripper like FETCH that could retract and attach to a CBM. (I) 5. To enable a soft capture and de-orbit of a piece of orbital debris will require self-aligning gripping and holding an object wherever possible (thermal coverings or shields of various materials, radiators, solar arrays, antenna dishes) with little or no residual power while adding either drag or active low level thrust.(K) 6. With the scalability of the FETCH technology, small satellites can be captured and handled or can incorporate FETCH gripper to dock to and handle other small vehicles and larger objects for de-orbiting or mitigating Orbital debris (L) 7. Many of previous MSFC and NASA proposals or concepts can now be realized or simplified by the development of the this initial and future FETCH grippers including commercial resupply, Exploration vehicle assembly, Satellite servicing, and orbital debris removal since a major part of these missions is to align to and capture some handle. Completed Project (2013 - 2014) Flexible Electrostatic Technology for Capture & Handling Project Center Innovation Fund: MSFC CIF Program | Space Technology Mission Directorate (STMD) For more information visit techport.nasa.gov Some NASA technology projects are smaller (for example SBIR/STTR, NIAC and Center Innovation Fund), and will have less content than other, larger projects. Newly created projects may not sensors or injection of permanent adhesives. With gripping forces estimated between 0.5 and 2.5 pounds per square inch or 70-300 lb./sq. ft. of surface contact, the FETCH can turn-on and turn-off rapidly and repeatedly to enable sample handling, soft docking, in-space assembly, and precision relocation for accurate anchor adhesion.
Global Regularity for the Fractional Euler Alignment System

NASA Astrophysics Data System (ADS)

Do, Tam; Kiselev, Alexander; Ryzhik, Lenya; Tan, Changhui

2018-04-01

We study a pressureless Euler system with a non-linear density-dependent alignment term, originating in the Cucker-Smale swarming models. The alignment term is dissipative in the sense that it tends to equilibrate the velocities. Its density dependence is natural: the alignment rate increases in the areas of high density due to species discomfort. The diffusive term has the order of a fractional Laplacian {(-partial _{xx})^{α/2}, α \\in (0, 1)}. The corresponding Burgers equation with a linear dissipation of this type develops shocks in a finite time. We show that the alignment nonlinearity enhances the dissipation, and the solutions are globally regular for all {α \\in (0, 1)}. To the best of our knowledge, this is the first example of such regularization due to the non-local nonlinear modulation of dissipation.
Attitude sensor alignment calibration for the solar maximum mission

NASA Technical Reports Server (NTRS)

Pitone, Daniel S.; Shuster, Malcolm D.

1990-01-01

An earlier heuristic study of the fine attitude sensors for the Solar Maximum Mission (SMM) revealed a temperature dependence of the alignment about the yaw axis of the pair of fixed-head star trackers relative to the fine pointing Sun sensor. Here, new sensor alignment algorithms which better quantify the dependence of the alignments on the temperature are developed and applied to the SMM data. Comparison with the results from the previous study reveals the limitations of the heuristic approach. In addition, some of the basic assumptions made in the prelaunch analysis of the alignments of the SMM are examined. The results of this work have important consequences for future missions with stringent attitude requirements and where misalignment variations due to variations in the temperature will be significant.
Alignments of Dark Matter Halos with Large-scale Tidal Fields: Mass and Redshift Dependence

NASA Astrophysics Data System (ADS)

Chen, Sijie; Wang, Huiyuan; Mo, H. J.; Shi, Jingjing

2016-07-01

Large-scale tidal fields estimated directly from the distribution of dark matter halos are used to investigate how halo shapes and spin vectors are aligned with the cosmic web. The major, intermediate, and minor axes of halos are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicular to the major axes of the tidal field. The strengths of these alignments generally increase with halo mass and redshift, but the dependence is only on the peak height, ν \\equiv {δ }{{c}}/σ ({M}{{h}},z). The scaling relations of the alignment strengths with the value of ν indicate that the alignment strengths remain roughly constant when the structures within which the halos reside are still in a quasi-linear regime, but decreases as nonlinear evolution becomes more important. We also calculate the alignments in projection so that our results can be compared directly with observations. Finally, we investigate the alignments of tidal tensors on large scales, and use the results to understand alignments of halo pairs separated at various distances. Our results suggest that the coherent structure of the tidal field is the underlying reason for the alignments of halos and galaxies seen in numerical simulations and in observations.
Relationship between field-aligned currents and inverted-V parallel potential drops observed at midaltitudes

NASA Astrophysics Data System (ADS)

Sakanoi, T.; Fukunishi, H.; Mukai, T.

1995-10-01

The inverted-V field-aligned acceleration region existing in the altitude range of several thousand kilometers plays an essential role for the magnetosphere-ionosphere coupling system. The adiabatic plasma theory predicts a linear relationship between field-aligned current density (J∥) and parallel potential drop (Φ∥), that is, J∥=KΦ∥, where K is the field-aligned conductance. We examined this relationship using the charged particle and magnetic field data obtained from the Akebono (Exos D) satellite. The potential drop above the satellite was derived from the peak energy of downward electrons, while the potential drop below the satellite was derived from two different methods: the peak energy of upward ions and the energy-dependent widening of electron loss cone. On the other hand, field-aligned current densities in the inverted-V region were estimated from the Akebono magnetometer data. Using these potential drops and field-aligned current densities, we estimated the linear field-aligned conductance KJΦ. Further, we obtained the corrected field-aligned conductance KCJΦ by applying the full Knight's formula to the current-voltage relationship. We also independently estimated the field-aligned conductance KTN from the number density and the thermal temperature of magnetospheric source electrons which were obtained by fitting accelerated Maxwellian functions for precipitating electrons. The results are summarized as follows: (1) The latitudinal dependence of parallel potential drops is characterized by a narrow V-shaped structure with a width of 0.4°-1.0°. (2) Although the inverted-V potential region exactly corresponds to the upward field aligned current region, the latitudinal dependence of upward current intensity is an inverted-U shape rather than an inverted-V shape. Thus it is suggested that the field-aligned conductance KCJΦ changes with a V-shaped latitudinal dependence. In many cases, KCJΦ values at the edge of the inverted-V region are about 5-10 times larger than those at the center. (3) By comparing KCJΦ with KTN, KCJΦ is found to be about 2-20 times larger than KTN. These results suggest that low-energy electrons such as trapped electrons, secondary and back-scattered electrons, and ionospheric electrons significantly contribute to upward field-aligned currents in the inverted-V region. It is therefore inferred that non adiabatic pitch angle scattering processes play an important role in the inverted-V region. .

Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I-type-II transition of natural band offsets in nonpolar zinc-blende AlxGa1 -xN /AlyGa1 -yN composites

NASA Astrophysics Data System (ADS)

Landmann, M.; Rauls, E.; Schmidt, W. G.

2017-04-01

The composition dependence of the natural band alignment at nonpolar AlxGa1 -xN /AlyGa1 -yN heterojunctions is investigated via hybrid functional based density functional theory. Accurate band-gap data are provided using Heyd-Scuseria-Ernzerhof (HSE) type hybrid functionals with a composition dependent exact-exchange contribution. The unstrained band alignment between zincblende (zb) AlxGa1 -xN semiconductor alloys is studied within the entire ternary composition range utilizing the Branch-point technique to align the energy levels related to the bulklike direct Γv→Γc and indirect, pseudodirect, respectively, Γv→Xc type transitions in zb-AlxGa1 -xN . While the zb-GaN/AlxGa1 -xN band edges consistently show a type-I alignment, the relative position of fundamental band edges changes to a type-II alignment in the Al-rich composition ranges of zb-AlxGa1 -xN /AlN and zb-AlxGa1 -xN /AlyGa1 -yN systems. The presence of a direct-indirect band-gap transition at xc=0.63 in zb-AlxGa1 -xN semiconductor alloys gives rise to a notably different composition dependence of band discontinuities in the direct and indirect energy-gap ranges. Below the critical direct-indirect Al/Ga-crossover concentration, the band offsets show a close to linear dependence on the alloy composition. In contrast, notable bowing characteristics of all band discontinuities are observed above the critical crossover composition.
Transiting circumbinary planets Kepler-34 b and Kepler-35 b.

PubMed

Welsh, William F; Orosz, Jerome A; Carter, Joshua A; Fabrycky, Daniel C; Ford, Eric B; Lissauer, Jack J; Prša, Andrej; Quinn, Samuel N; Ragozzine, Darin; Short, Donald R; Torres, Guillermo; Winn, Joshua N; Doyle, Laurance R; Barclay, Thomas; Batalha, Natalie; Bloemen, Steven; Brugamyer, Erik; Buchhave, Lars A; Caldwell, Caroline; Caldwell, Douglas A; Christiansen, Jessie L; Ciardi, David R; Cochran, William D; Endl, Michael; Fortney, Jonathan J; Gautier, Thomas N; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer R; Holman, Matthew J; Howard, Andrew W; Howell, Steve B; Isaacson, Howard; Jenkins, Jon M; Klaus, Todd C; Latham, David W; Li, Jie; Marcy, Geoffrey W; Mazeh, Tsevi; Quintana, Elisa V; Robertson, Paul; Shporer, Avi; Steffen, Jason H; Windmiller, Gur; Koch, David G; Borucki, William J

2012-01-11

Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
Ultrafast direct electron transfer at organic semiconductor and metal interfaces.

PubMed

Xiang, Bo; Li, Yingmin; Pham, C Huy; Paesani, Francesco; Xiong, Wei

2017-11-01

The ability to control direct electron transfer can facilitate the development of new molecular electronics, light-harvesting materials, and photocatalysis. However, control of direct electron transfer has been rarely reported, and the molecular conformation-electron dynamics relationships remain unclear. We describe direct electron transfer at buried interfaces between an organic polymer semiconductor film and a gold substrate by observing the first dynamical electric field-induced vibrational sum frequency generation (VSFG). In transient electric field-induced VSFG measurements on this system, we observe dynamical responses (<150 fs) that depend on photon energy and polarization, demonstrating that electrons are directly transferred from the Fermi level of gold to the lowest unoccupied molecular orbital of organic semiconductor. Transient spectra further reveal that, although the interfaces are prepared without deliberate alignment control, a subensemble of surface molecules can adopt conformations for direct electron transfer. Density functional theory calculations support the experimental results and ascribe the observed electron transfer to a flat-lying polymer configuration in which electronic orbitals are found to be delocalized across the interface. The present observation of direct electron transfer at complex interfaces and the insights gained into the relationship between molecular conformations and electron dynamics will have implications for implementing novel direct electron transfer in energy materials.
Enhanced Lighting Techniques and Augmented Reality to Improve Human Task Performance

NASA Technical Reports Server (NTRS)

Maida, James C.; Bowen, Charles K.; Pace, John W.

2005-01-01

One of the most versatile tools designed for use on the International Space Station (ISS) is the Special Purpose Dexterous Manipulator (SPDM) robot. Operators for this system are trained at NASA Johnson Space Center (JSC) using a robotic simulator, the Dexterous Manipulator Trainer (DMT), which performs most SPDM functions under normal static Earth gravitational forces. The SPDM is controlled from a standard Robotic Workstation. A key feature of the SPDM and DMT is the Force/Moment Accommodation (FMA) system, which limits the contact forces and moments acting on the robot components, on its payload, an Orbital Replaceable Unit (ORU), and on the receptacle for the ORU. The FMA system helps to automatically alleviate any binding of the ORU as it is inserted or withdrawn from a receptacle, but it is limited in its correction capability. A successful ORU insertion generally requires that the reference axes of the ORU and receptacle be aligned to within approximately 0.25 inch and 0.5 degree of nominal values. The only guides available for the operator to achieve these alignment tolerances are views from any available video cameras. No special registration markings are provided on the ORU or receptacle, so the operator must use their intrinsic features in the video display to perform the pre-insertion alignment task. Since optimum camera views may not be available, and dynamic orbital lighting conditions may limit viewing periods, long times are anticipated for performing some ORU insertion or extraction operations. This study explored the feasibility of using augmented reality (AR) to assist with SPDM operations. Geometric graphical symbols were overlaid on the end effector (EE) camera view to afford cues to assist the operator in attaining adequate pre-insertion ORU alignment.
Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

DOE PAGES

Wang, Xu; Le, Anh -Thu; Yu, Chao; ...

2016-03-30

We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. Lastly, amore » simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.« less
Investigation of the two-quasiparticle bands in the doubly-odd nucleus 166Ta using a particle-number conserving cranked shell model

NASA Astrophysics Data System (ADS)

Zhang, ZhenHua

2016-07-01

The high-spin rotational properties of two-quasiparticle bands in the doubly-odd 166Ta are analyzed using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency hω are reproduced very well by the particle-number conserving calculations, which provides a reliable support to the configuration assignments in previous works for these bands. The backbendings in these two-quasiparticle bands are analyzed by the calculated occupation probabilities and the contributions of each orbital to the total angular momentum alignments. The moments of inertia and alignments for the Gallagher-Moszkowski partners of these observed two-quasiparticle rotational bands are also predicted.
Observational Constraints on the Orbit and Location of Planet Nine in the Outer Solar System

NASA Astrophysics Data System (ADS)

Brown, Michael E.; Batygin, Konstantin

2016-06-01

We use an extensive suite of numerical simulations to constrain the mass and orbit of Planet Nine, the recently proposed perturber in a distant eccentric orbit in the outer solar system. We compare our simulations to the observed population of aligned eccentric high semimajor axis Kuiper belt objects (KBOs) and determine which simulation parameters are statistically compatible with the observations. We find that only a narrow range of orbital elements can reproduce the observations. In particular, the combination of semimajor axis, eccentricity, and mass of Planet Nine strongly dictates the semimajor axis range of the orbital confinement of the distant eccentric KBOs. Allowed orbits, which confine KBOs with semimajor axis beyond 380 au, have perihelia roughly between 150 and 350 au, semimajor axes between 380 and 980 au, and masses between 5 and 20 Earth masses. Orbitally confined objects also generally have orbital planes similar to that of the planet, suggesting that the planet is inclined approximately 30°to the ecliptic. We compare the allowed orbital positions and estimated brightness of Planet Nine to previous and ongoing surveys which would be sensitive to the planet’s detection and use these surveys to rule out approximately two-thirds of the planet’s orbit. Planet Nine is likely near aphelion with an approximate brightness of 22< V< 25. At opposition, its motion, mainly due to parallax, can easily be detected within 24 hours.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Jason W.; Van Eyken, Julian C.; Jackson, Brian K.

PTFO 8-8695b represents the first transiting exoplanet candidate orbiting a pre-main-sequence star (van Eyken et al. 2012, ApJ, 755, 42). We find that the unusual lightcurve shapes of PTFO 8-8695 can be explained by transits of a planet across an oblate, gravity-darkened stellar disk. We develop a theoretical framework for understanding precession of a planetary orbit's ascending node for the case when the stellar rotational angular momentum and the planetary orbital angular momentum are comparable in magnitude. We then implement those ideas to simultaneously and self-consistently fit two separate lightcurves observed in 2009 December and 2010 December. Our two self-consistentmore » fits yield M{sub p} = 3.0 M{sub Jup} and M{sub p} = 3.6 M{sub Jup} for assumed stellar masses of M{sub *} = 0.34 M{sub Sun} and M{sub *} = 0.44 M{sub Sun} respectively. The two fits have precession periods of 293 days and 581 days. These mass determinations (consistent with previous upper limits) along with the strength of the gravity-darkened precessing model together validate PTFO 8-8695b as just the second hot Jupiter known to orbit an M-dwarf. Our fits show a high degree of spin-orbit misalignment in the PTFO 8-8695 system: 69 Degree-Sign {+-} 2 Degree-Sign or 73. Degree-Sign 1 {+-} 0. Degree-Sign 5, in the two cases. The large misalignment is consistent with the hypothesis that planets become hot Jupiters with random orbital plane alignments early in a system's lifetime. We predict that as a result of the highly misaligned, precessing system, the transits should disappear for months at a time over the course of the system's precession period. The precessing, gravity-darkened model also predicts other observable effects: changing orbit inclination that could be detected by radial velocity observations, changing stellar inclination that would manifest as varying vsin i, changing projected spin-orbit alignment that could be seen by the Rossiter-McLaughlin effect, changing transit shapes over the course of the precession, and differing lightcurves as a function of wavelength. Our measured planet radii of 1.64 R{sub Jup} and 1.68 R{sub Jup} in each case are consistent with a young, hydrogen-dominated planet that results from a ''hot-start'' formation mechanism.« less
Optimizing exoplanet transit searches

NASA Astrophysics Data System (ADS)

Herrero, E.; Ribas, I.; Jordi, C.

2013-05-01

Exoplanet searches using the transit technique are nowadays providing a great number of findings. Most exoplanet transit detection programs that are currently underway are focused on large catalogs of stars with no pre-selection. This necessarily makes such surveys quite inefficient, because huge amounts of data are processed for a relatively low transiting planet yield. In this work we investigate a method to increase the efficiency of a targeted exoplanet search with the transit technique by preselecting a subset of candidates from large catalogs of stars. Assuming spin-orbit alignment, this can be done by considering stars that have higher probability to be oriented nearly equator-on (inclination close to 90°). We use activity-rotation velocity relations for low-mass stars to study the dependence of the position in the activity - v sin(i) diagram on the stellar axis inclination. We compose a catalog of G-, K-, M-type main sequence simulated stars using isochrones, an isotropic inclination distribution and empirical relations to obtain their rotation periods and activity indexes. Then the activity-vsini diagram is filled and statistics are applied to trace the areas containing the higher ratio of stars with inclinations above 80°. A similar statistics is applied to stars from real catalogs with log(R'_{HK}) and v sin(i) data to find their probability of being equator-on. We present the method used to generate the simulated star catalog and the subsequent statistics to find the highly inclined stars from real catalogs using the activity-v sin(i) diagram. Several catalogs from the literature are analysed and a subsample of stars with the highest probability of being equator-on is presented. Assuming spin-orbit alignment, the efficiency of an exoplanet transit search in the resulting subsample of probably highly inclined stars is estimated to be two to three times higher than with a global search with no pre-selection.
Orbital-dependent Electron-Hole Interaction in Graphene and Associated Multi-Layer Structures

PubMed Central

Deng, Tianqi; Su, Haibin

2015-01-01

We develop an orbital-dependent potential to describe electron-hole interaction in materials with structural 2D character, i.e. quasi-2D materials. The modulated orbital-dependent potentials are also constructed with non-local screening, multi-layer screening, and finite gap due to the coupling with substrates. We apply the excitonic Hamiltonian in coordinate-space with developed effective electron-hole interacting potentials to compute excitons’ binding strength at M (π band) and Γ (σ band) points in graphene and its associated multi-layer forms. The orbital-dependent potential provides a range-separated property for regulating both long- and short-range interactions. This accounts for the existence of the resonant π exciton in single- and bi-layer graphenes. The remarkable strong electron-hole interaction in σ orbitals plays a decisive role in the existence of σ exciton in graphene stack at room temperature. The interplay between gap-opening and screening from substrates shed a light on the weak dependence of σ exciton binding energy on the thickness of graphene stacks. Moreover, the analysis of non-hydrogenic exciton spectrum in quasi-2D systems clearly demonstrates the remarkable comparable contribution of orbital dependent potential with respect to non-local screening process. The understanding of orbital-dependent potential developed in this work is potentially applicable for a wide range of materials with low dimension. PMID:26610715
Implied alignment: a synapomorphy-based multiple-sequence alignment method and its use in cladogram search

NASA Technical Reports Server (NTRS)

Wheeler, Ward C.

2003-01-01

A method to align sequence data based on parsimonious synapomorphy schemes generated by direct optimization (DO; earlier termed optimization alignment) is proposed. DO directly diagnoses sequence data on cladograms without an intervening multiple-alignment step, thereby creating topology-specific, dynamic homology statements. Hence, no multiple-alignment is required to generate cladograms. Unlike general and globally optimal multiple-alignment procedures, the method described here, implied alignment (IA), takes these dynamic homologies and traces them back through a single cladogram, linking the unaligned sequence positions in the terminal taxa via DO transformation series. These "lines of correspondence" link ancestor-descendent states and, when displayed as linearly arrayed columns without hypothetical ancestors, are largely indistinguishable from standard multiple alignment. Since this method is based on synapomorphy, the treatment of certain classes of insertion-deletion (indel) events may be different from that of other alignment procedures. As with all alignment methods, results are dependent on parameter assumptions such as indel cost and transversion:transition ratios. Such an IA could be used as a basis for phylogenetic search, but this would be questionable since the homologies derived from the implied alignment depend on its natal cladogram and any variance, between DO and IA + Search, due to heuristic approach. The utility of this procedure in heuristic cladogram searches using DO and the improvement of heuristic cladogram cost calculations are discussed. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.
Device for coupling a first vehicle to a second vehicle

NASA Technical Reports Server (NTRS)

Rudmann, A. A. (Inventor)

1980-01-01

A device is disclosed, carried by a first vehicle such as an orbiting space shuttle, having a plurality of contact members for engaging and holding an annular ring on a second vehicle such as an orbiting payload. The contact members are connected to manipulator arms which are mounted at a fulcrum point and which are moved by an iris type mechanism. Movement of the manipulator arms causes the contact members to grasp or release the annular ring. Bumper devices are provided to axially align the annular ring and draw the contact members into engagement therewith.
Energy level alignment at molecule-metal interfaces from an optimally tuned range-separated hybrid functional

DOE PAGES

Liu, Zhen-Fei; Egger, David A.; Refaely-Abramson, Sivan; ...

2017-02-21

The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. Here, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by constructionmore » captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, the both the level alignment and work function changes. This approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.« less
An optimal beam alignment method for large-scale distributed space surveillance radar system

NASA Astrophysics Data System (ADS)

Huang, Jian; Wang, Dongya; Xia, Shuangzhi

2018-06-01

Large-scale distributed space surveillance radar is a very important ground-based equipment to maintain a complete catalogue for Low Earth Orbit (LEO) space debris. However, due to the thousands of kilometers distance between each sites of the distributed radar system, how to optimally implement the Transmitting/Receiving (T/R) beams alignment in a great space using the narrow beam, which proposed a special and considerable technical challenge in the space surveillance area. According to the common coordinate transformation model and the radar beam space model, we presented a two dimensional projection algorithm for T/R beam using the direction angles, which could visually describe and assess the beam alignment performance. Subsequently, the optimal mathematical models for the orientation angle of the antenna array, the site location and the T/R beam coverage are constructed, and also the beam alignment parameters are precisely solved. At last, we conducted the optimal beam alignment experiments base on the site parameters of Air Force Space Surveillance System (AFSSS). The simulation results demonstrate the correctness and effectiveness of our novel method, which can significantly stimulate the construction for the LEO space debris surveillance equipment.
Energy level alignment at molecule-metal interfaces from an optimally tuned range-separated hybrid functional

NASA Astrophysics Data System (ADS)

Liu, Zhen-Fei; Egger, David A.; Refaely-Abramson, Sivan; Kronik, Leeor; Neaton, Jeffrey B.

2017-03-01

The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. In this work, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by construction captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, the both the level alignment and work function changes. Our approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.
Effects of Disk Warping on the Inclination Evolution of Star-Disk-Binary Systems

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2018-04-01

Several recent studies have suggested that circumstellar disks in young stellar binaries may be driven into misalignement with their host stars due to secular gravitational interactions between the star, disk and the binary companion. The disk in such systems is twisted/warped due to the gravitational torques from the oblate central star and the external companion. We calculate the disk warp profile, taking into account of bending wave propagation and viscosity in the disk. We show that for typical protostellar disk parameters, the disk warp is small, thereby justifying the "flat-disk" approximation adopted in previous theoretical studies. However, the viscous dissipation associated with the small disk warp/twist tends to drive the disk toward alignment with the binary or the central star. We calculate the relevant timescales for the alignment. We find the alignment is effective for sufficiently cold disks with strong external torques, especially for systems with rapidly rotating stars, but is ineffective for the majority of star-disk-binary systems. Viscous warp driven alignment may be necessary to account for the observed spin-orbit alignment in multi-planet systems if these systems are accompanied by an inclined binary companion.
Effects of disc warping on the inclination evolution of star-disc-binary systems

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2018-07-01

Several recent studies have suggested that circumstellar discs in young stellar binaries may be driven into misalignement with their host stars due to the secular gravitational interactions between the star, disc, and the binary companion. The disc in such systems is twisted/warped due to the gravitational torques from the oblate central star and the external companion. We calculate the disc warp profile, taking into account the bending wave propagation and viscosity in the disc. We show that for typical protostellar disc parameters, the disc warp is small, thereby justifying the `flat-disc' approximation adopted in previous theoretical studies. However, the viscous dissipation associated with the small disc warp/twist tends to drive the disc towards alignment with the binary or the central star. We calculate the relevant time-scales for the alignment. We find that the alignment is effective for sufficiently cold discs with strong external torques, especially for systems with rapidly rotating stars, but is ineffective for the majority of the star-disc-binary systems. Viscous warp-driven alignment may be necessary to account for the observed spin-orbit alignment in multiplanet systems if these systems are accompanied by an inclined binary companion.
Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Trihalide Perovskite Interface - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Przepioski, Joshua

2015-08-25

This work correlates resonant peaks from first principles calculation on ammonia (NH 3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH 3NH 3PbI 3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI2 and the poly(9,9-dioctylfluorene-2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to better identify themore » dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.« less
Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Iodide Perovskite Interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Przepioski, Joshua

2015-08-28

This work correlates resonant peaks from first principles calculation on ammonia (NH 3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH 3NH 3PbI 3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI 2 and the poly(9,9-dioctylfluorene- 2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to bettermore » identify the dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)

Cegla, H. M.; Watson, C. A.; Oshagh, M.

Observations of the Rossiter–McLaughlin (RM) effect provide information on star–planet alignments, which can inform planetary migration and evolution theories. Here, we go beyond the classical RM modeling and explore the impact of a convective blueshift that varies across the stellar disk and non-Gaussian stellar photospheric profiles. We simulated an aligned hot Jupiter with a four-day orbit about a Sun-like star and injected center-to-limb velocity (and profile shape) variations based on radiative 3D magnetohydrodynamic simulations of solar surface convection. The residuals between our modeling and classical RM modeling were dependent on the intrinsic profile width and v sin i; the amplitudemore » of the residuals increased with increasing v sin i and with decreasing intrinsic profile width. For slowly rotating stars the center-to-limb convective variation dominated the residuals (with amplitudes of 10 s of cm s{sup −1} to ∼1 m s{sup −1}); however, for faster rotating stars the dominant residual signature was due a non-Gaussian intrinsic profile (with amplitudes from 0.5 to 9 m s{sup −1}). When the impact factor was 0, neglecting to account for the convective center-to-limb variation led to an uncertainty in the obliquity of ∼10°–20°, even though the true v sin i was known. Additionally, neglecting to properly model an asymmetric intrinsic profile had a greater impact for more rapidly rotating stars (e.g., v sin i = 6 km s{sup −1}) and caused systematic errors on the order of ∼20° in the measured obliquities. Hence, neglecting the impact of stellar surface convection may bias star–planet alignment measurements and consequently theories on planetary migration and evolution.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tripathi, Anjali; Winn, Joshua N.; De Kleer, Katherine R.

We present new spectroscopic and photometric observations of the transiting exoplanetary system WASP-3. Spectra obtained during two separate transits exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the sky-projected angle between the planetary orbital axis and the stellar rotation axis, {lambda} = 3.3{sup +2.5}{sub -4.4} deg. This alignment between the axes suggests that WASP-3b has a low orbital inclination relative to the equatorial plane of its parent star. During our first night of spectroscopic measurements, we observed an unexpected redshift briefly exceeding the expected sum of the orbital and RM velocities by 140 m s{sup -1}. This anomalymore » could represent the occultation of material erupting from the stellar photosphere, although it is more likely to be an artifact caused by moonlight scattered into the spectrograph.« less
Characterization of the IMF By-dependent field-aligned currents in the cleft region based on DE 2 observations

NASA Technical Reports Server (NTRS)

Taguchi, S.; Sugiura, M.; Winningham, J. D.; Slavin, J. A.

1993-01-01

The magnetic field and plasma data from 47 passes of DE-2 are used to study the IMF By-dependent distribution of field-aligned currents in the cleft region. It is proposed that the low-latitude cleft current (LCC) region is not an extension of the region 1 or region 2 current system and that a pair of LCCs and high-latitude cleft currents (HCCs) constitutes the cleft field-aligned current regime. The proposed pair of cleft field-aligned currents is explained with a qualitative model in which this pair of currents is generated on open field lines that have just been reconnected on the dayside magnetopause. The electric fields are transmitted along the field lines to the ionosphere, creating a poleward electric field and a pair of field-aligned currents when By is positive; the pair of field-aligned currents consists of a downward current at lower latitudes and an upward current at higher latitudes. In the By negative case, the model explains the reversal of the field-aligned current direction in the LCC and HCC regions.
The Solar Wind as a Magnetofluid Turbulence Laboratory

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.

2011-01-01

The solar wind is the Sun's exosphere. As the solar atmosphere expands into interplanetary space, it is accelerated and heated. Data from spacecraft located throughout the heliosphere have revealed that this exosphere has velocities of several hundred kilometers/sec, densities at Earth orbit of about 5 particles/cu cm, and an entrained magnetic field that at Earth orbit that is about 5 10-5 Gauss. A fascinating feature of the solar wind is that the magnetic field fluctuates in a way that is highly reminiscent of "Alfven waves, i.e., the fluctuating magnetic fields are more-or-less aligned with fluctuations in the velocity of the plasma and, with proper normalization, have approximately equal magnitudes. The imperfect (observed) alignment leads to a variety of complex interactions. In many respects, the flow patterns appear to be an example of fully developed magneto fluid turbulence. Recently, the dissipation range of this turbulence has been studied using search coil magnetometer data from the STAFF instrument on the four Cluster spacecraft. I will attempt to give an overview of selected properties of this large-scale and small-scale turbulence.
Ground and CHAMP observations of field-aligned current circuits generated by lower atmospheric disturbances and expectations to the SWARM to clarify their three dimensional structure

NASA Astrophysics Data System (ADS)

Iyemori, Toshihiko; Nakanishi, Kunihito; Aoyama, Tadashi; Lühr, Hermann

2014-05-01

Acoustic gravity waves propagated to the ionosphere cause dynamo currents in the ionosphere. They divert along geomagnetic field lines of force to another hemisphere accompanying electric field and then flow in the ionosphere of another hemisphere by the electric field forming closed current circuits. The oscillating current circuits with the period of acoustic waves generate magnetic variations on the ground, and they are observed as long period geomagnetic pulsations. This effect has been detected during big earthquakes, strong typhoons, tornados etc. On a low-altitude satellite orbit, the spatial distribution (i.e., structure) of the current circuits along the satellite orbit should be detected as temporal magnetic oscillations, and the effect is confirmed by a CHAMP data analysis. On the spatial structure, in particular, in the longitudinal direction, it has been difficult to examine by a single satellite or from ground magnetic observations. The SWARM satellites will provide an unique opportunity to clarify the three dimensional structure of the field-aligned current circuits.
Optical Modeling Activities for NASA's James Webb Space Telescope (JWST). 4; Overview and Introduction of Matlab Based Toolkits used to Interface with Optical Design Software

NASA Technical Reports Server (NTRS)

Howard, Joseph

2007-01-01

This is part four of a series on the ongoing optical modeling activities for James Webb Space Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory. The work here introduces some of the math software tools used to perform the work of the previous three papers of this series. NASA has recently approved these in-house tools for public release as open source, so this presentation also serves as a quick tutorial on their use. The tools are collections of functions written in Matlab, which interface with optical design software (CodeV, OSLO, and Zemax) using either COM or DDE communication protocol. The functions are discussed, and examples are given.
Optical modeling activities for NASA's James Webb Space Telescope (JWST): IV. Overview and introduction of MATLAB based toolkits used to interface with optical design software

NASA Astrophysics Data System (ADS)

Howard, Joseph M.

2007-09-01

This paper is part four of a series on the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two papers discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third paper investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory. The work here introduces some of the math software tools used to perform the work of the previous three papers of this series. NASA has recently approved these in-house tools for public release as open source, so this presentation also serves as a quick tutorial on their use. The tools are collections of functions written for use in MATLAB to interface with optical design software (CODE V, OSLO, and ZEMAX) using either COM or DDE communication protocol. The functions are discussed, and examples are given.
Space Science

NASA Image and Video Library

1995-06-08

Scientists at Marshall's Adaptive Optics Lab demonstrate the Wave Front Sensor alignment using the Phased Array Mirror Extendible Large Aperture (PAMELA) optics adjustment. The primary objective of the PAMELA project is to develop methods for aligning and controlling adaptive optics segmented mirror systems. These systems can be used to acquire or project light energy. The Next Generation Space Telescope is an example of an energy acquisition system that will employ segmented mirrors. Light projection systems can also be used for power beaming and orbital debris removal. All segmented optical systems must be adjusted to provide maximum performance. PAMELA is an on going project that NASA is utilizing to investigate various methods for maximizing system performance.
Telescope Multi-Field Wavefront Control with a Kalman Filter

NASA Technical Reports Server (NTRS)

Lou, John Z.; Redding, David; Sigrist, Norbert; Basinger, Scott

2008-01-01

An effective multi-field wavefront control (WFC) approach is demonstrated for an actuated, segmented space telescope using wavefront measurements at the exit pupil, and the optical and computational implications of this approach are discussed. The integration of a Kalman Filter as an optical state estimator into the wavefront control process to further improve the robustness of the optical alignment of the telescope will also be discussed. Through a comparison of WFC performances between on-orbit and ground-test optical system configurations, the connection (and a possible disconnection) between WFC and optical system alignment under these circumstances are analyzed. Our MACOS-based computer simulation results will be presented and discussed.
Imaging the Ultrafast Photoelectron Transfer Process in Alizarin-TiO2.

PubMed

Gomez, Tatiana; Hermann, Gunter; Zarate, Ximena; Pérez-Torres, Jhon Fredy; Tremblay, Jean Christophe

2015-07-30

In this work, we adopt a quantum mechanical approach based on time-dependent density functional theory (TDDFT) to study the optical and electronic properties of alizarin supported on TiO2 nano-crystallites, as a prototypical dye-sensitized solar cell. To ensure proper alignment of the donor (alizarin) and acceptor (TiO2 nano-crystallite) levels, static optical excitation spectra are simulated using time-dependent density functional theory in response. The ultrafast photoelectron transfer from the dye to the cluster is simulated using an explicitly time-dependent, one-electron TDDFT ansatz. The model considers the δ-pulse excitation of a single active electron localized in the dye to the complete set of energetically accessible, delocalized molecular orbitals of the dye/nano-crystallite complex. A set of quantum mechanical tools derived from the transition electronic flux density is introduced to visualize and analyze the process in real time. The evolution of the created wave packet subject to absorbing boundary conditions at the borders of the cluster reveal that, while the electrons of the aromatic rings of alizarin are heavily involved in an ultrafast charge redistribution between the carbonyl groups of the dye molecule, they do not contribute positively to the electron injection and, overall, they delay the process.
Aligning Plasma-Arc Welding Oscillations

NASA Technical Reports Server (NTRS)

Norris, Jeff; Fairley, Mike

1989-01-01

Tool aids in alignment of oscillator probe on variable-polarity plasma-arc welding torch. Probe magnetically pulls arc from side to side as it moves along joint. Tensile strength of joint depends on alignment of weld bead and on alignment of probe. Operator installs new tool on front of torch body, levels it with built-in bubble glass, inserts probe in slot on tool, and locks probe in place. Procedure faster and easier and resulting alignment more accurate and repeatable.
Pair aligning improved motility of Quincke rollers.

PubMed

Lu, Shi Qing; Zhang, Bing Yue; Zhang, Zhi Chao; Shi, Yan; Zhang, Tian Hui

2018-06-06

Density-dependent speed is studied in a two-dimensional active colloid in which the colloidal particles are propelled by an external electric field via a Quincke rotation. Above the critcal electric field, dense dynamic clusters form spotaneously, in which the particles are highly aligned in velocity and move much faster than isolated units. Detailed observations on pair collision reveal that the alignment of velocity is induced by the long-ranged hydrodynamic interactions and the improvement of speed in the clusters arises from pair aligning in which two particles are closely paired and rotate synchronically. In the aligning state, the short-range in-plane dipole-dipole attraction enhances the rotation torque and gives rises to a larger rolling speed. The pair aligning becomes difficult and unstable at high electric field where the normal dipole-dipole repulsion becomes dominant. As a consequence, the dependence of speed on density becomes weak increasingly upon the increase of the electric field. This result offers an interpretation for the discrepancy between our and previous observations on Quincke rollers.
The direction of stretch-induced cell and stress fiber orientation depends on collagen matrix stress.

PubMed

Tondon, Abhishek; Kaunas, Roland

2014-01-01

Cell structure depends on both matrix strain and stiffness, but their interactive effects are poorly understood. We investigated the interactive roles of matrix properties and stretching patterns on cell structure by uniaxially stretching U2OS cells expressing GFP-actin on silicone rubber sheets supporting either a surface-adsorbed coating or thick hydrogel of type-I collagen. Cells and their actin stress fibers oriented perpendicular to the direction of cyclic stretch on collagen-coated sheets, but oriented parallel to the stretch direction on collagen gels. There was significant alignment parallel to the direction of a steady increase in stretch for cells on collagen gels, while cells on collagen-coated sheets did not align in any direction. The extent of alignment was dependent on both strain rate and duration. Stretch-induced alignment on collagen gels was blocked by the myosin light-chain kinase inhibitor ML7, but not by the Rho-kinase inhibitor Y27632. We propose that active orientation of the actin cytoskeleton perpendicular and parallel to direction of stretch on stiff and soft substrates, respectively, are responses that tend to maintain intracellular tension at an optimal level. Further, our results indicate that cells can align along directions of matrix stress without collagen fibril alignment, indicating that matrix stress can directly regulate cell morphology.
Changes in Rod and Frame Test Scores Recorded in Schoolchildren during Development – A Longitudinal Study

PubMed Central

Bagust, Jeff; Docherty, Sharon; Haynes, Wayne; Telford, Richard; Isableu, Brice

2013-01-01

The Rod and Frame Test has been used to assess the degree to which subjects rely on the visual frame of reference to perceive vertical (visual field dependence- independence perceptual style). Early investigations found children exhibited a wide range of alignment errors, which reduced as they matured. These studies used a mechanical Rod and Frame system, and presented only mean values of grouped data. The current study also considered changes in individual performance. Changes in rod alignment accuracy in 419 school children were measured using a computer-based Rod and Frame test. Each child was tested at school Grade 2 and retested in Grades 4 and 6. The results confirmed that children displayed a wide range of alignment errors, which decreased with age but did not reach the expected adult values. Although most children showed a decrease in frame dependency over the 4 years of the study, almost 20% had increased alignment errors suggesting that they were becoming more frame-dependent. Plots of individual variation (SD) against mean error allowed the sample to be divided into 4 groups; the majority with small errors and SDs; a group with small SDs, but alignments clustering around the frame angle of 18°; a group showing large errors in the opposite direction to the frame tilt; and a small number with large SDs whose alignment appeared to be random. The errors in the last 3 groups could largely be explained by alignment of the rod to different aspects of the frame. At corresponding ages females exhibited larger alignment errors than males although this did not reach statistical significance. This study confirms that children rely more heavily on the visual frame of reference for processing spatial orientation cues. Most become less frame-dependent as they mature, but there are considerable individual differences. PMID:23724139
Spline screw payload fastening system

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1993-01-01

A system for coupling an orbital replacement unit (ORU) to a space station structure via the actions of a robot and/or astronaut is described. This system provides mechanical and electrical connections both between the ORU and the space station structure and between the ORU and the ORU and the robot/astronaut hand tool. Alignment and timing features ensure safe, sure handling and precision coupling. This includes a first female type spline connector selectively located on the space station structure, a male type spline connector positioned on the orbital replacement unit so as to mate with and connect to the first female type spline connector, and a second female type spline connector located on the orbital replacement unit. A compliant drive rod interconnects the second female type spline connector and the male type spline connector. A robotic special end effector is used for mating with and driving the second female type spline connector. Also included are alignment tabs exteriorally located on the orbital replacement unit for berthing with the space station structure. The first and second female type spline connectors each include a threaded bolt member having a captured nut member located thereon which can translate up and down the bolt but are constrained from rotation thereabout, the nut member having a mounting surface with at least one first type electrical connector located on the mounting surface for translating with the nut member. At least one complementary second type electrical connector on the orbital replacement unit mates with at least one first type electrical connector on the mounting surface of the nut member. When the driver on the robotic end effector mates with the second female type spline connector and rotates, the male type spline connector and the first female type spline connector lock together, the driver and the second female type spline connector lock together, and the nut members translate up the threaded bolt members carrying the first type electrical connector up to the complementary second type connector for interconnection therewith.
On-Orbit Lunar Modulation Transfer Function Measurements for the Moderate Resolution Imaging Spectroradiometer

NASA Technical Reports Server (NTRS)

Choi, Taeyong; Xiong, Xiaoxiong; Wang, Zhipeng

2013-01-01

Spatial quality of an imaging sensor can be estimated by evaluating its modulation transfer function (MTF) from many different sources such as a sharp edge, a pulse target, or bar patterns with different spatial frequencies. These well-defined targets are frequently used for prelaunch laboratory tests, providing very reliable and accurate MTF measurements. A laboratory-quality edge input source was included in the spatial-mode operation of the Spectroradiometric Calibration Assembly (SRCA), which is one of the onboard calibrators of the Moderate Resolution Imaging Spectroradiometer (MODIS). Since not all imaging satellites have such an instrument, SRCA MTF estimations can be used as a reference for an on-orbit lunar MTF algorithm and results. In this paper, the prelaunch spatial quality characterization process from the Integrated Alignment Collimator and SRCA is briefly discussed. Based on prelaunch MTF calibration using the SRCA, a lunar MTF algorithm is developed and applied to the lifetime on-orbit Terra and Aqua MODIS lunar collections. In each lunar collection, multiple scan-directionMoon-to-background transition profiles are aligned by the subpixel edge locations from a parametric Fermi function fit. Corresponding accumulated edge profiles are filtered and interpolated to obtain the edge spread function (ESF). The MTF is calculated by applying a Fourier transformation on the line spread function through a simple differentiation of the ESF. The lifetime lunar MTF results are analyzed and filtered by a relationship with the Sun-Earth-MODIS angle. Finally, the filtered lunarMTF values are compared to the SRCA MTF results. This comparison provides the level of accuracy for on-orbit MTF estimations validated through prelaunch SRCA measurements. The lunar MTF values had larger uncertainty than the SRCA MTF results; however, the ratio mean of lunarMTF fit and SRCA MTF values is within 2% in the 250- and 500-m bands. Based on the MTF measurement uncertainty range, the suggested lunar MTF algorithm can be applied to any on-orbit imaging sensor with lunar calibration capability.
Effect of deformation and orientation on spin orbit density dependent nuclear potential

NASA Astrophysics Data System (ADS)

Mittal, Rajni; Kumar, Raj; Sharma, Manoj K.

2017-11-01

Role of deformation and orientation is investigated on spin-orbit density dependent part VJ of nuclear potential (VN=VP+VJ) obtained within semi-classical Thomas Fermi approach of Skyrme energy density formalism. Calculations are performed for 24-54Si+30Si reactions, with spherical target 30Si and projectiles 24-54Si having prolate and oblate shapes. The quadrupole deformation β2 is varying within range of 0.023 ≤ β2 ≤0.531 for prolate and -0.242 ≤ β2 ≤ -0.592 for oblate projectiles. The spin-orbit dependent potential gets influenced significantly with inclusion of deformation and orientation effect. The spin-orbit barrier and position gets significantly influenced by both the sign and magnitude of β2-deformation. Si-nuclei with β22<0 have higher spin-orbit barrier (compact spin-orbit configuration) in comparison to systems with β2>0. The possible role of spin-orbit potential on barrier characteristics such as barrier height, barrier curvature and on the fusion pocket is also probed. In reference to prolate and oblate systems, the angular dependence of spin-orbit potential is further studied on fusion cross-sections.
Solar dynamic power for Space Station Freedom

NASA Technical Reports Server (NTRS)

Labus, Thomas L.; Secunde, Richard R.; Lovely, Ronald G.

1989-01-01

The Space Station Freedom Program is presently planned to consist of two phases. At the completion of Phase 1, Freedom's manned base will consist of a transverse boom with attached manned modules and 75 kW of available electric power supplied by photovoltaic (PV) power sources. In Phase 2, electric power available to the manned base will be increased to 125 kW by the addition of two solar dynamic (SD) power modules, one at each end of the transverse boom. Power for manned base growth beyond Phase 2 will be supplied by additional SD modules. Studies show that SD power for the growth eras will result in life cycle cost savings of $3 to $4 billion when compared to PV-supplied power. In the SD power modules for Space Station Freedom, an offset parabolic concentrator collects and focuses solar energy into a heat receiver. To allow full power operation over the entire orbit, the receiver includes integral thermal energy storage by means of the heat of fusion of a salt mixture. Thermal energy is removed from the receiver and converted to electrical energy by a power conversion unit (PCU) which includes a closed brayton cycle (CBC) heat engine and an alternator. The receiver/PCU/radiator combination will be completely assembled and charged with gas and cooling fluid on earth before launch to orbit. The concentrator subassemblies will be pre-aligned and stowed in the orbiter bay before launch. On orbit, the receiver/PCU/radiator assembly will be installed as a unit. The pre-aligned concentrator panels will then be latched together and the total concentrator attached to the receiver/PCU/radiator by the astronauts. After final electric connections are made and checkout is complete, the SD power module will be ready for operation.
Solar dynamic power for space station freedom

NASA Technical Reports Server (NTRS)

Labus, Thomas L.; Secunde, Richard R.; Lovely, Ronald G.

1989-01-01

The Space Station Freedom Program is presently planned to consist of two phases. At the completion of Phase 1, Freedom's manned base will consist of a transverse boom with attached manned modules and 75 kW of available electric power supplied by photovoltaic (PV) power sources. In Phase 2, electric power available to the manned base will be increased to 125 kW by the addition of two solar dynamic (SD) power modules, one at each end of the transverse boom. Power for manned base growth beyond Phase 2 will be supplied by additional SD modules. Studies show that SD power for the growth eras will result in life cycle cost savings of $3 to $4 billion when compared to PV-supplied power. In the SD power modules for Space Station Freedom, an offset parabolic concentrator collects and focuses solar energy into a heat receiver. To allow full power operation over the entire orbit, the receiver includes integral thermal energy storage by means of the heat of fusion of a salt mixture. Thermal energy is removed from the receiver and converted to electrical energy by a power conversion unit (PCU) which includes a closed brayton cycle (CBC) heat engine and an alternator. The receiver/PCU/radiator combination will be completely assembled and charged with gas and cooling fluid on Earth before launch to orbit. The concentrator subassemblies will be pre-aligned and stowed in the orbiter bay before launch. On orbit, the receiver/PCU/radiator assembly will be installed as a unit. The pre-aligned concentrator panels will then be latched together and the total concentrator attached to the receiver/PCU/radiator by the astronauts. After final electric connections are made and checkout is complete, the SD power module will be ready for operation.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlaufman, Kevin C., E-mail: kcs@ucolick.or

Of the 26 transiting exoplanet systems with measurements of the Rossiter-McLaughlin (RM) effect, eight have now been found to be significantly spin-orbit misaligned in the plane of the sky (i.e., RM misalignment angle |{lambda}| {approx}> 30{sup 0} and inconsistent with {lambda} = 0{sup 0}). Unfortunately, the RM effect does not constrain the complement misalignment angle between the orbit of the planet and the spin of its host star along the line of sight (LOS). I use a simple model of stellar rotation benchmarked with observational data to statistically identify 10 exoplanet systems from a sample of 75 for which theremore » is likely a significant degree of spin-orbit misalignment along the LOS: HAT-P-7, HAT-P-14, HAT-P-16, HD 17156, Kepler-5, Kepler-7, TrES-4, WASP-1, WASP-12, and WASP-14. All 10 systems have host stellar masses M {sub *} in the range 1.2 M {sub sun} {approx}< M {sub *} {approx}< 1.5 M {sub sun}, and the probability of this occurrence by chance is less than one in ten thousand. In addition, the planets in the candidate-misaligned systems are preferentially massive and eccentric. The coupled distribution of misalignment from the RM effect and from this analysis suggests that transiting exoplanets are more likely to be spin-orbit aligned than expected given predictions for a transiting planet population produced entirely by planet-planet scattering or Kozai cycles and tidal friction. For that reason, there are likely two populations of close-in exoplanet systems: a population of aligned systems and a population of apparently misaligned systems in which the processes that lead to misalignment or to the survival of misaligned systems operate more efficiently in systems with massive stars and planets.« less
Energy level alignment at the methylammonium lead iodide/copper phthalocyanine interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Shi; Goh, Teck Wee; Sum, Tze Chien, E-mail: Alfred@ntu.edu.sg, E-mail: Tzechien@ntu.edu.sg

2014-08-01

The energy level alignment at the CH{sub 3}NH{sub 3}PbI{sub 3}/copper phthalocyanine (CuPc) interface is investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). XPS reveal a 0.3 eV downward band bending in the CuPc film. UPS validate this finding and further reveal negligible interfacial dipole formation – verifying the viability of vacuum level alignment. The highest occupied molecular orbital of CuPc is found to be closer to the Fermi level than the valance band maximum of CH{sub 3}NH{sub 3}PbI{sub 3}, facilitating hole transfer from CH{sub 3}NH{sub 3}PbI{sub 3} to CuPc. However, subsequent hole extraction from CuPc may bemore » impeded by the downward band bending in the CuPc layer.« less

Alignment in star-debris disc systems seen by Herschel

NASA Astrophysics Data System (ADS)

Greaves, J. S.; Kennedy, G. M.; Thureau, N.; Eiroa, C.; Marshall, J. P.; Maldonado, J.; Matthews, B. C.; Olofsson, G.; Barlow, M. J.; Moro-Martín, A.; Sibthorpe, B.; Absil, O.; Ardila, D. R.; Booth, M.; Broekhoven-Fiene, H.; Brown, D. J. A.; Cameron, A. Collier; del Burgo, C.; Di Francesco, J.; Eislöffel, J.; Duchêne, G.; Ertel, S.; Holland, W. S.; Horner, J.; Kalas, P.; Kavelaars, J. J.; Lestrade, J.-F.; Vican, L.; Wilner, D. J.; Wolf, S.; Wyatt, M. C.

2014-02-01

Many nearby main-sequence stars have been searched for debris using the far-infrared Herschel satellite, within the DEBRIS, DUNES and Guaranteed-Time Key Projects. We discuss here 11 stars of spectral types A-M where the stellar inclination is known and can be compared to that of the spatially resolved dust belts. The discs are found to be well aligned with the stellar equators, as in the case of the Sun's Kuiper belt, and unlike many close-in planets seen in transit surveys. The ensemble of stars here can be fitted with a star-disc tilt of ≲ 10°. These results suggest that proposed mechanisms for tilting the star or disc in fact operate rarely. A few systems also host imaged planets, whose orbits at tens of au are aligned with the debris discs, contrary to what might be expected in models where external perturbers induce tilts.
The place of the Local Group in the cosmic web

NASA Astrophysics Data System (ADS)

Forero-Romero, Jaime E.; González, Roberto

2016-10-01

We use the Bolshoi Simulation to find the most probable location of the Local Group (LG) in the cosmic web. Our LG simulacra are pairs of halos with isolation and kinematic properties consistent with observations. The cosmic web is defined using a tidal tensor approach. We find that the LG's preferred location is regions with a dark matter overdensity close to the cosmic average. This makes filaments and sheets the preferred environment. We also find a strong alignment between the LG and the cosmic web. The orbital angular momentum is preferentially perpendicular to the smallest tidal eigenvector, while the vector connecting the two halos is strongly aligned along the the smallest tidal eigenvector and perpendicular to the largest tidal eigenvector; the pair lies and moves along filaments and sheets. We do not find any evidence for an alignment between the spin of each halo in the pair and the cosmic web.
BRIGHTEST SATELLITE GALAXY ALIGNMENT OF SLOAN DIGITAL SKY SURVEY GALAXY GROUPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhigang; Wang Yougang; Chen Xuelei

2013-05-01

We study the alignment signal between the distribution of the brightest satellite galaxies (BSGs) and the major axes of their host groups using the Sloan Digital Sky Survey group catalog constructed by Yang et al. After correcting for the effect of group ellipticity, a statistically significant ({approx}5{sigma}) major-axis alignment is detected and the alignment angle is found to be 43. Degree-Sign 0 {+-} 0. Degree-Sign 4. More massive and richer groups show a stronger BSG alignment. The BSG alignment around blue brightest central galaxies (BCGs) is slightly stronger than that around red BCGs. Red BSGs have a much stronger major-axismore » alignment than blue BSGs. Unlike BSGs, other satellites do not show very significant alignment with their group's major axis. We further explore BSG alignment using the semi-analytic model (SAM) constructed by Guo et al. In general, we found good agreement of the model with observations: BSGs in the SAM show a strong major-axis alignment that depends on group mass and richness in the same way as in observations and none of the other satellites exhibit prominent alignment. However, a discrepancy also exists in that the SAM shows a BSG color dependence opposite of that in observations, which is most probably induced by a missing large-scale environment ingredient in the SAM. The combination of two popular scenarios can explain the BSG alignment we detected. First, satellites merged into the group along the surrounding filaments, which are strongly aligned with the major axis of the group. Second, BSGs entered their host group more recently than other satellites, so they have preserved more information about their assembling history and major-axis alignment. In the SAM, we found positive evidence for the second scenario in the fact that BSGs merged into groups statistically more recently than other satellites. We also found that most of the BSGs (80%) were BCGs before they merged into groups and earlier merging BSGs tend to be closer to their BCGs than other BSGs. On the other hand, although the BSG color dependence in observations is the opposite of that in the SAM, it might also indicate that the first scenario is a good explanation.« less
CALIBRATION OF EQUILIBRIUM TIDE THEORY FOR EXTRASOLAR PLANET SYSTEMS. II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Brad M. S., E-mail: hansen@astro.ucla.edu

2012-09-20

We present a new empirical calibration of equilibrium tidal theory for extrasolar planet systems, extending a prior study by incorporating detailed physical models for the internal structure of planets and host stars. The resulting strength of the stellar tide produces a coupling that is strong enough to reorient the spins of some host stars without causing catastrophic orbital evolution, thereby potentially explaining the observed trend in alignment between stellar spin and planetary orbital angular momentum. By isolating the sample whose spins should not have been altered in this model, we also show evidence for two different processes that contribute tomore » the population of planets with short orbital periods. We apply our results to estimate the remaining lifetimes for short-period planets, examine the survival of planets around evolving stars, and determine the limits for circularization of planets with highly eccentric orbits. Our analysis suggests that the survival of circularized planets is strongly affected by the amount of heat dissipated, which is often large enough to lead to runaway orbital inflation and Roche lobe overflow.« less
Stability Analysis of the Planetary System Orbiting Upsilon Andromedae. 2; Simulations Using New Lick Observatory Fits

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Rivera, Eugenio J.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting upsilon Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on recent fits to the radial velocity data obtained by the planet search group at Lick Observatory. The new fits result in significantly more stable systems than did the initially announced planetary parameters. Our integrations using the 2000 February parameters show that if the system is nearly planar, then it is stable for at least 100 Myr for m(sub f) = 1/sin i less than or = 4. In some stable systems, the eccentricity of the inner planet experiences large oscillations. The relative periastra of the outer two planets' orbits librate about 0 deg. in most of the stable systems; if future observations imply that the periastron longitudes of these planets are very closely aligned at the present epoch, dynamical simulations may provide precise estimates for the masses and orbital inclinations of these two planets.
On trajectories of rolling marbles in cones and other funnels

NASA Astrophysics Data System (ADS)

White, Gary D.

2013-12-01

We report on theoretical and experimental results for a ball that rolls without slipping on a surface of revolution, whose symmetry axis is aligned with a uniform gravitational field, particularly investigating both near-circular orbits and scattering-type orbits in cones. The experimental data give support for the theoretical treatment, a non-trivial application of Newton's second law that expands on our previous work and related work of others. Our findings refine those from a recent article in this journal, and largely replicate those obtained from an earlier Lagrangian approach, adding some new details and commentary. While the orbits of marbles rolling in cones do not match inverse-square-law orbits quantitatively (e.g., instead of Kepler's 3rd law, we have T2∝R), we argue that students should experience these qualitative phenomena—precession of orbits, escape velocity behavior, spin-orbit coupling, conservation laws for angular momentum, energy, and spin projection—as much for the fun and kinesthetic impressions as for the raw learning. We also report on a heretofore largely ignored variable in the exploration of rolling orbits in a gravity well: the marble's spin about its own axis as it rolls. Experimenters can, intentionally or not, vary this initial condition and produce different orbital periods for a given orbital radius—a distinctly non-celestial behavior. Careful selection of the initial spin direction and speed for a particular cone can result in marble orbits that mimic the planetary ellipses.
Cooperative Search of Autonomous Vehicles for Unknown Targets

NASA Astrophysics Data System (ADS)

Yang, Sheng Qing; Yu, Jian Qiao; Zhang, Si Yu

2013-01-01

We study the orbital-dependent superconducting pairing in a five-orbital t-J1-J2 model for iron pnictides. Depending on the orbital selectivity of electron correlations and the orbital characters along the Fermi surface, the superconducting gap in an A_{1g} pairing state may exhibit anisotropy. This anisotropy varies with the degree of J1-J2 magnetic frustration. We have also calculated the dynamical spin susceptibility in the superconducting state. The frequency dependence of the susceptibility at the antiferromagnetic wavevector (\\pi,0) shows a resonance, whose width is enhanced by the orbital dependence of the superconducting gap; when the latter is sufficiently strong, the resonance peak may be split into two. We discuss the implications of our results on the recent angle-resolved photoemission and neutron-scattering measurements in several superconducting iron pnictides.
Focus determination for the James Webb Space Telescope Science Instruments: A Survey of Methods

NASA Technical Reports Server (NTRS)

Davila, Pamela S.; Bolcar, Matthew R.; Boss, B.; Dean, B.; Hapogian, J.; Howard, J.; Unger, B.; Wilson, M.

2006-01-01

The James Webb Space Telescope (JWST) is a segmented deployable telescope that will require on-orbit alignment using the Near Infrared Camera as a wavefront sensor. The telescope will be aligned by adjusting seven degrees of freedom on each of 18 primary mirror segments and five degrees of freedom on the secondary mirror to optimize the performance of the telescope and camera at a wavelength of 2 microns. With the completion of these adjustments, the telescope focus is set and the optical performance of each of the other science instruments should then be optimal without making further telescope focus adjustments for each individual instrument. This alignment approach requires confocality of the instruments after integration and alignment to the composite metering structure, which will be verified during instrument level testing at Goddard Space Flight Center with a telescope optical simulator. In this paper, we present the results from a study of several analytical approaches to determine the focus for each instrument. The goal of the study is to compare the accuracies obtained for each method, and to select the most feasible for use during optical testing.
A novel perovskite solar cell design using aligned TiO2 nano-bundles grown on a sputtered Ti layer and a benzothiadiazole-based, dopant-free hole-transporting material.

PubMed

Ameen, Sadia; Nazim, M; Akhtar, M Shaheer; Nazeeruddin, Mohammad Khaja; Shin, Hyung-Shik

2017-11-16

This work highlights the utilization of a novel hole-transporting material (HTM) derived from benzothiadiazole: 4-(3,5-bis(trifluoromethyl)phenyl)-7-(5'-hexyl-[2,2'-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole (CF-BTz-ThR) and aligned TiO 2 nano-bundles (TiO 2 NBs) as the electron transporting layer (ETL) for perovskite solar cells (PSCs). The aligned TiO 2 NBs were grown on titanium (Ti)-coated FTO substrates using a facile hydrothermal method. The newly designed CF-BTz-ThR molecule with suitable highest occupied molecular orbital (HOMO) favored the effective hole injection from perovskite deposited aligned TiO 2 NBs thin film. The PSCs demonstrated a power conversion efficiency (PCE) of ∼15.4% with a short circuit current density (J sc ) of ∼22.42 mA cm -2 and an open circuit voltage (V oc ) of ∼1.02 V. The efficiency data show the importance of proper molecular engineering whilst highlighting the advantages of dopant-free HTMs in PSCs.
Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. 3; Measurement for URSA Minor

NASA Technical Reports Server (NTRS)

Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

2005-01-01

This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field contains a quasi-stellar object that serves as the "reference point". Integrating the motion of Ursa Minor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 40 (10, 76) and 89 (78, 160) kpc, respectively, where the values in the parentheses represent the 95% confidence intervals derived from Monte Carlo experiments. The eccentricity of the orbit is 0.39 (0.09, 0.79), and the orbital period is 1.5 (1.1, 2.7) Gyr. The orbit is retrograde and inclined by 124 degrees (94 deg, 36 deg ) to the Galactic plane. Ursa Minor is not a likely member of a proposed stream of galaxies on similar orbits around the Milky Way, nor is the plane of its orbit coincident with a recently proposed planar alignment of galaxies around the Milky Way. Comparing the orbits of Ursa Minor and Carina shows no reason for the different star formation histories of these two galaxies. Ursa Minor must contain dark matter to have a high probability of having survived disruption by the Galactic tidal force until the present.
High altitude observations of Birkeland currents

NASA Technical Reports Server (NTRS)

Russell, C. T.

1977-01-01

Several models of field-aligned currents (Birkeland currents) in the magnetosphere are discussed, and high altitude observations of these currents, carried out with the aid of highly eccentric earth-orbiting spacecraft of the OGO and IMP series, are reviewed. The essential roles of Birkeland currents are identified: they relieve charge imbalances, transmit stresses, and lead to particle acceleration anomalous resistivity.
Tidal alignment of galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact ofmore » smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.« less
Tidal alignment of galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš, E-mail: blazek@berkeley.edu, E-mail: zvlah@stanford.edu, E-mail: useljak@berkeley.edu

We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact ofmore » smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used 'nonlinear alignment model,' finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the 'GI' term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.« less
Periastron advance in spinning black hole binaries: Gravitational self-force from numerical relativity

NASA Astrophysics Data System (ADS)

Le Tiec, Alexandre; Buonanno, Alessandra; Mroué, Abdul H.; Pfeiffer, Harald P.; Hemberger, Daniel A.; Lovelace, Geoffrey; Kidder, Lawrence E.; Scheel, Mark A.; Szilágyi, Bela; Taylor, Nicholas W.; Teukolsky, Saul A.

2013-12-01

We study the general relativistic periastron advance in spinning black hole binaries on quasicircular orbits, with spins aligned or antialigned with the orbital angular momentum, using numerical-relativity simulations, the post-Newtonian approximation, and black hole perturbation theory. By imposing a symmetry by exchange of the bodies’ labels, we devise an improved version of the perturbative result and use it as the leading term of a new type of expansion in powers of the symmetric mass ratio. This allows us to measure, for the first time, the gravitational self-force effect on the periastron advance of a nonspinning particle orbiting a Kerr black hole of mass M and spin S=-0.5M2, down to separations of order 9M. Comparing the predictions of our improved perturbative expansion with the exact results from numerical simulations of equal-mass and equal-spin binaries, we find a remarkable agreement over a wide range of spins and orbital separations.
Polarization-dependent DANES study on vertically-aligned ZnO nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Chengjun; Park, Chang-In; Jin, Zhenlan

2016-05-01

The local structural and local density of states of vertically-aligned ZnO nanorods were examined by using a polarization-dependent diffraction anomalous near edge structure (DANES) measurements from c-oriented ZnO nanorods at the Zn K edge with the incident x-ray electric field parallel and perpendicular to the x-ray momentum transfer direction. Orientation-dependent local structures determined by DANES were comparable with polarization-dependent EXAFS results. Unlike other techniques, polarization-dependent DANES can uniquely describe the orientation-dependent local structural properties and the local density of states of a selected element in selected-phased crystals of compounds or mixed-phased structures.
On the Impact of Widening Vector Registers on Sequence Alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daily, Jeffrey A.; Kalyanaraman, Anantharaman; Krishnamoorthy, Sriram

2016-09-22

Vector extensions, such as SSE, have been part of the x86 since the 1990s, with applications in graphics, signal processing, and scientific applications. Although many algorithms and applications can naturally benefit from automatic vectorization techniques, there are still many that are difficult to vectorize due to their dependence on irregular data structures, dense branch operations, or data dependencies. Sequence alignment, one of the most widely used operations in bioinformatics workflows, has a computational footprint that features complex data dependencies. In this paper, we demonstrate that the trend of widening vector registers adversely affects the state-of-the-art sequence alignment algorithm based onmore » striped data layouts. We present a practically efficient SIMD implementation of a parallel scan based sequence alignment algorithm that can better exploit wider SIMD units. We conduct comprehensive workload and use case analyses to characterize the relative behavior of the striped and scan approaches and identify the best choice of algorithm based on input length and SIMD width.« less
Ellipticity dependence of the near-threshold harmonics of H2 in an elliptical strong laser field.

PubMed

Yang, Hua; Liu, Peng; Li, Ruxin; Xu, Zhizhan

2013-11-18

We study the ellipticity dependence of the near-threshold (NT) harmonics of pre-aligned H2 molecules using the time-dependent density functional theory. The anomalous maximum appearing at a non-zero ellipticity for the generated NT harmonics can be attributed to multiphoton effects of the orthogonally polarized component of the elliptical driving laser field. Our calculation also shows that the structure of the bound-state, such as molecular alignment and bond length, can be sensitively reflected on the ellipticity dependence of the near-threshold harmonics.
Recovering Neptune 170 Years After its Initial Discovery

NASA Astrophysics Data System (ADS)

Myles, Justin

2017-01-01

Recent work by Trujillo and Shephard (2014) and Batygin and Brown (2016) has shown an as-yet unexplained clustering of the periapse vectors of the most distant Kuiper Belt objects. This unusual clustering has motivated the search for an unseen perturbing planet that is responsible for maintaining the alignment. As a proof of concept of a technique for locating unseen solar system planets, we use dynamical N-body integrations to simulate the orbital dynamics of distant Kuiper Belt objects, with the aim of determining the orbital parameters of Neptune (which, for the sake of exercise, we assume is, as-yet, undiscovered). In this poster, we determine the accuracy with which the perturbing planet’s orbital elements and sky location can be determined, and we show how the lessons learned can improve the search strategy for potentially undiscovered trans-Neptunian planets.
Cassini Orbit Trim Maneuvers at Saturn - Overview of Attitude Control Flight Operations

NASA Technical Reports Server (NTRS)

Burk, Thomas A.

2011-01-01

The Cassini spacecraft has been in orbit around Saturn since July 1, 2004. To remain on the planned trajectory which maximizes science data return, Cassini must perform orbit trim maneuvers using either its main engine or its reaction control system thrusters. Over 200 maneuvers have been executed on the spacecraft since arrival at Saturn. To improve performance and maintain spacecraft health, changes have been made in maneuver design command placement, in accelerometer scale factor, and in the pre-aim vector used to align the engine gimbal actuator prior to main engine burn ignition. These and other changes have improved maneuver performance execution errors significantly since 2004. A strategy has been developed to decide whether a main engine maneuver should be performed, or whether the maneuver can be executed using the reaction control system.
Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Alff, W. H.

1980-01-01

The feasibility and costs were determined for a 1 m to 30 m diameter ambient temperature, infrared to submillimeter orbiting astronomical telescope which is to be shuttle-deployed, free-flying, and have a 10 year orbital life. Baseline concepts, constraints on delivery and deployment, and the sunshield required are examined. Reflector concepts, the optical configuration, alignment and pointing, and materials are also discussed. Technology studies show that a 10 m to 30 m diameter system which is background and diffraction limited at 30 micron m is feasible within the stated time frame. A 10 m system is feasible with current mirror technology, while a 30 m system requires technology still in development.

Correlational Effects of the Molecular-Tilt Configuration and the Intermolecular van der Waals Interaction on the Charge Transport in the Molecular Junction.

PubMed

Shin, Jaeho; Gu, Kyungyeol; Yang, Seunghoon; Lee, Chul-Ho; Lee, Takhee; Jang, Yun Hee; Wang, Gunuk

2018-06-25

Molecular conformation, intermolecular interaction, and electrode-molecule contacts greatly affect charge transport in molecular junctions and interfacial properties of organic devices by controlling the molecular orbital alignment. Here, we statistically investigated the charge transport in molecular junctions containing self-assembled oligophenylene molecules sandwiched between an Au probe tip and graphene according to various tip-loading forces ( F L ) that can control the molecular-tilt configuration and the van der Waals (vdW) interactions. In particular, the molecular junctions exhibited two distinct transport regimes according to the F L dependence (i.e., F L -dependent and F L -independent tunneling regimes). In addition, the charge-injection tunneling barriers at the junction interfaces are differently changed when the F L ≤ 20 nN. These features are associated to the correlation effects between the asymmetry-coupling factor (η), the molecular-tilt angle (θ), and the repulsive intermolecular vdW force ( F vdW ) on the molecular-tunneling barriers. A more-comprehensive understanding of these charge transport properties was thoroughly developed based on the density functional theory calculations in consideration of the molecular-tilt configuration and the repulsive vdW force between molecules.
Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

PubMed Central

Yuan, Kai-Jun; Bandrauk, André D.

2015-01-01

We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785
Observational Evidence for Tidal Interaction in Close Binary Systems

NASA Astrophysics Data System (ADS)

Mazeh, T.

This paper reviews the rich corpus of observational evidence for tidal effects, mostly based on photometric and radial-velocity measurements. This is done in a period when the study of binaries is being revolutionized by large-scaled photometric surveys that are detecting many thousands of new binaries and tens of extrasolar planets. We begin by examining the short-term effects, such as ellipsoidal variability and apsidal motion. We next turn to the long-term effects, of which circularization was studied the most: a transition period between circular and eccentric orbits has been derived for eight coeval samples of binaries. The study of synchronization and spin-orbit alignment is less advanced. As binaries are supposed to reach synchronization before circularization, one can expect finding eccentric binaries in pseudo-synchronization state, the evidence for which is reviewed. We also discuss synchronization in PMS and young stars, and compare the emerging timescale with the circularization timescale. We next examine the tidal interaction in close binaries that are orbited by a third distant companion, and review the effect of pumping the binary eccentricity by the third star. We elaborate on the impact of the pumped eccentricity on the tidal evolution of close binaries residing in triple systems, which may shrink the binary separation. Finally we consider the extrasolar planets and the observational evidence for tidal interaction with their parent stars. This includes a mechanism that can induce radial drift of short-period planets, either inward or outward, depending on the planetary radial position relative to the corotation radius. Another effect is the circularization of planetary orbits, the evidence for which can be found in eccentricity-versus-period plot of the planets already known. Whenever possible, the paper attempts to address the possible confrontation between theory and observations, and to point out noteworthy cases and observations that can be performed in the future and may shed some light on the key questions that remain open.
Atmospheric lidar co-alignment sensor: flight model electro-optical characterization campaign

NASA Astrophysics Data System (ADS)

Valverde Guijarro, Ángel Luis; Belenguer Dávila, Tomás.; Laguna Hernandez, Hugo; Ramos Zapata, Gonzalo

2017-10-01

Due to the difficulty in studying the upper layer of the troposphere by using ground-based instrumentation, the conception of a space-orbit atmospheric LIDAR (ATLID) becomes necessary. ATLID born in the ESA's EarthCare Programme framework as one of its payloads, being the first instrument of this kind that will be in the Space. ATLID will provide vertical profiles of aerosols and thin clouds, separating the relative contribution of aerosol and molecular scattering to know aerosol optical depth. It operates at a wavelength of 355 nm and has a high spectral resolution receiver and depolarization channel with a vertical resolution up to 100m from ground to an altitude of 20 km and, and up to 500m from 20km to 40km. ATLID measurements will be done from a sun-synchronous orbit at 393 km altitude, and an alignment (co-alignment) sensor (CAS) is revealed as crucial due to the way in which LIDAR analyses the troposphere. As in previous models, INTA has been in charge of part of the ATLID instrument co-alignment sensor (ATLID-CAS) electro-optical characterization campaign. CAS includes a set of optical elements to take part of the useful signal, to direct it onto the memory CCD matrix (MCCD) used for the co-alignment determination, and to focus the selected signal on the MCCD. Several tests have been carried out for a proper electro-optical characterization: CAS line of sight (LoS) determination and stability, point spread function (PSF), absolute response (AbsRes), pixel response non uniformity (PRNU), response linearity (ResLin) and spectral response. In the following lines, a resume of the flight model electrooptical characterization campaign is reported on. In fact, results concerning the protoflight model (CAS PFM) will be summarized. PFM requires flight-level characterization, so most of the previously mentioned tests must be carried out under simulated working conditions, i.e., the vacuum level (around 10-5 mbar) and temperature range (between 50°C and -30°C) that are expected during ATLID Space operation.
Dynamical Properties of Eccentric Nuclear Disks: Stability, Longevity, and Implications for Tidal Disruption Rates in Post-merger Galaxies

NASA Astrophysics Data System (ADS)

Madigan, Ann-Marie; Halle, Andrew; Moody, Mackenzie; McCourt, Michael; Nixon, Chris; Wernke, Heather

2018-02-01

In some galaxies, the stars orbiting the supermassive black hole take the form of an eccentric nuclear disk, in which every star is on a coherent, apsidally aligned orbit. The most famous example of an eccentric nuclear disk is the double nucleus of Andromeda, and there is strong evidence for many more in the local universe. Despite their apparent ubiquity, however, a dynamical explanation for their longevity has remained a mystery: differential precession should wipe out large-scale apsidal-alignment on a short timescale. Here we identify a new dynamical mechanism which stabilizes eccentric nuclear disks, and explain for the first time the negative eccentricity gradient seen in the Andromeda nucleus. The stabilizing mechanism drives oscillations of the eccentricity vectors of individual orbits, both in direction (about the mean body of the disk) and in magnitude. Combined with the negative eccentricity gradient, the eccentricity oscillations push some stars near the inner edge of the disk extremely close to the black hole, potentially leading to tidal disruption events (TDEs). Order of magnitude calculations predict extremely high rates in recently formed eccentric nuclear disks (∼0.1–1 {{yr}}-1 {{gal}}-1). Unless the stellar disks are replenished, these rates should decrease with time as the disk depletes in mass. If eccentric nuclear disks form during gas-rich major mergers, this may explain the preferential occurrence of TDEs in recently merged and post-merger (E+A/K+A) galaxies.
Qualification of the Tropical Rainfall Measuring Mission Solar Array Deployment System

NASA Technical Reports Server (NTRS)

Lawrence, Jon

1998-01-01

The Tropical Rainfall Measuring Mission (TRMM) solar arrays are placed into orbital configuration by a complex deployment system. Its two wings each comprise twin seven square solar panels located by a twelve foot articulated boom. The four spring-driven hinge lines per wing are rate-limited by viscous dampers. The wings are stowed against the spacecraft kinematically, and released by five pyrotechnically-actuated mechanisms. Since deployment failure would be catastrophic, a total of 17 deployment tests were completed to qualify the system for the worst cast launch environment. This successful testing culminated in the flawless deployment of the solar arrays on orbit, 15 minutes after launch in November 1997. The custom gravity negation system used to perform deployment testing is modular to allow its setup in several locations, including the launch site in Japan. Both platform and height can be varied, to meet the requirements of the test configuration and the test facility. Its air pad floatation system meets tight packaging requirements, allowing installation while stowed against the spacecraft without breaking any flight interfaces, and avoiding interference during motion. This system was designed concurrently with the deployment system, to facilitate its installation, to aid in the integration of the flight system to the spacecraft, while demonstrating deployment capabilities. Critical parameters for successful testing were alignment of deployment axes and tables to gravity, alignment of table seams to minimize discontinuities, and minimizing pressure drops in the air supply system. Orbital performance was similar to that predicted by ground testing.
Atomic-scale inversion of spin polarization at an organic-antiferromagnetic interface

NASA Astrophysics Data System (ADS)

Caffrey, Nuala M.; Ferriani, Paolo; Marocchi, Simone; Heinze, Stefan

2013-10-01

Using first-principles calculations, we show that the magnetic properties of a two-dimensional antiferromagnetic transition-metal surface are modified on the atomic scale by the adsorption of small organic molecules. We consider benzene (C6H6), cyclooctatetraene (C8H8), and a small transition-metal-benzene complex (BzV) adsorbed on a single atomic layer of Mn deposited on the W(110) surface—a surface which exhibits a nearly antiferromagnetic alignment of the magnetic moments in adjacent Mn rows. Due to the spin dependent hybridization of the molecular pz orbitals with the d states of the Mn monolayer, there is a significant reduction of the magnetic moments in the Mn film. Furthermore, the spin polarization at this organic-antiferromagnetic interface is found to be modulated on the atomic scale, both enhanced and inverted, as a result of the molecular adsorption. We show that this effect can be resolved by spin-polarized scanning tunneling microscopy (SP-STM). Our simulated SP-STM images display a spatially dependent spin resolved vacuum charge density above an adsorbed molecule—i.e., different regions above the molecule sustain different signs of spin polarization. While states with s and p symmetry dominate the vacuum charge density in the vicinity of the Fermi energy for the clean magnetic surface, we demonstrate that after a molecule is adsorbed those d states, which are normally suppressed due to their symmetry, can play a crucial role in the vacuum due to their interaction with the molecular orbitals. We also model the effect of small deviations from perfect antiferromagnetic ordering, induced by the slight canting of magnetic moments due to the spin spiral ground state of Mn/W(110).
Phased Array Mirror Extendible Large Aperture (PAMELA) Optics Adjustment

NASA Technical Reports Server (NTRS)

1995-01-01

Scientists at Marshall's Adaptive Optics Lab demonstrate the Wave Front Sensor alignment using the Phased Array Mirror Extendible Large Aperture (PAMELA) optics adjustment. The primary objective of the PAMELA project is to develop methods for aligning and controlling adaptive optics segmented mirror systems. These systems can be used to acquire or project light energy. The Next Generation Space Telescope is an example of an energy acquisition system that will employ segmented mirrors. Light projection systems can also be used for power beaming and orbital debris removal. All segmented optical systems must be adjusted to provide maximum performance. PAMELA is an on going project that NASA is utilizing to investigate various methods for maximizing system performance.
Searching for gravitational waves from compact binaries with precessing spins

NASA Astrophysics Data System (ADS)

Harry, Ian; Privitera, Stephen; Bohé, Alejandro; Buonanno, Alessandra

2016-07-01

Current searches for gravitational waves from compact-object binaries with the LIGO and Virgo observatories employ waveform models with spins aligned (or antialigned) with the orbital angular momentum. Here, we derive a new statistic to search for compact objects carrying generic (precessing) spins. Applying this statistic, we construct banks of both aligned- and generic-spin templates for binary black holes and neutron star-black hole binaries, and compare the effectualness of these banks towards simulated populations of generic-spin systems. We then use these banks in a pipeline analysis of Gaussian noise to measure the increase in background incurred by using generic- instead of aligned-spin banks. Although the generic-spin banks have roughly a factor of ten more templates than the aligned-spin banks, we find an overall improvement in signal recovery at a fixed false-alarm rate for systems with high-mass ratio and highly precessing spins. This gain in sensitivity comes at a small loss of sensitivity (≲4 %) for systems that are already well covered by aligned-spin templates. Since the observation of even a single binary merger with misaligned spins could provide unique astrophysical insights into the formation of these sources, we recommend that the method described here be developed further to mount a viable search for generic-spin binary mergers in LIGO/Virgo data.
How does the Structure of Spherical Dark Matter Halos Affect the Types of Orbits in Disk Galaxies?

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.

The main objective of this work is to determine the character of orbits of stars moving in the meridional (R,z) plane of an axially symmetric time-independent disk galaxy model with a central massive nucleus and an additional spherical dark matter halo component. In particular, we try to reveal the influence of the scale length of the dark matter halo on the different families of orbits of stars, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when this parameter varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish safely bet ween ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Our numerical computations reveal that when the dark matter halo is highly concentrated, that is when the scale length has low values the vast majority of star orbits move in regular orbits, while on the oth er hand in less concentrated dark matter halos the percentage of chaos increases significantly. We also compared our results with early related work.
A record of astronomically forced climate change in a late Ordovician (Sandbian) deep marine sequence, Ordos Basin, North China

NASA Astrophysics Data System (ADS)

Fang, Qiang; Wu, Huaichun; Hinnov, Linda A.; Wang, Xunlian; Yang, Tianshui; Li, Haiyan; Zhang, Shihong

2016-07-01

The late Ordovician Pingliang Formation on the southwestern margin of the Ordos Basin, North China, consists of rhythmic alternations of shale, limestone, and siliceous beds. To explore the possible astronomical forcing preserved in this lithological record, continuous lithological rank and magnetic susceptibility (MS) stratigraphic series were obtained from a 34 m thick section of the Pingliang Formation at Guanzhuang. Power spectral analysis of the MS and rank series reveal 85.5 cm to 124 cm, 23 cm to 38 cm, and 15 cm to 27 cm thick sedimentary cycles that in ratio match that of late Ordovician short eccentricity, obliquity and precession astronomical cycles. The power spectrum of the MS time series, calibrated to interpreted short orbital eccentricity cycles, aligns with spectral peaks to astronomical parameters, including 95 kyr short orbital eccentricity, 35.3 kyr and 30.6 kyr obliquity, and 19.6 kyr and 16.3 kyr precession cycles. The 15 cm to 27 cm thick limestone-shale couplets mainly represent precession cycles, and siliceous bed deposition may be related to both precession and obliquity forcing. We propose that precession-forced sea-level fluctuations mainly controlled production of lime mud in a shallow marine environment, and transport to the basin. Precession and obliquity controlled biogenic silica productivity, and temperature-dependent preservation of silica may have been influenced by obliquity forcing.
Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films.

PubMed

Bukusoglu, Emre; Martinez-Gonzalez, Jose A; Wang, Xiaoguang; Zhou, Ye; de Pablo, Juan J; Abbott, Nicholas L

2017-12-06

We report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic-BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau-de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations assumed by BPs in thin films reflect a complex interplay of surface interactions and elastic energies associated with strain of the BP lattice. The results also provide new principles and methods to control the structure and properties of BP thin films, which may find use in BP-templated material synthesis, and BP-based optical and electronic devices.
Utopia Cracks and Polygons

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-339, 23 April 2003
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.
Magnetospheric-ionospheric Poynting flux

NASA Technical Reports Server (NTRS)

Thayer, Jeffrey P.

1994-01-01

Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchis-Ojeda, Roberto; Winn, Joshua N.; Carter, Joshua A.

We present photometry of four transits of the exoplanet WASP-4b, each with a precision of approximately 500 ppm and a time sampling of 40-60 s. We have used the data to refine the estimates of the system parameters and ephemerides. During two of the transits we observed a short-lived, low-amplitude anomaly that we interpret as the occultation of a starspot by the planet. We also found evidence for a pair of similar anomalies in previously published photometry. The recurrence of these anomalies suggests that the stellar rotation axis is nearly aligned with the orbital axis, or else the starspot wouldmore » not have remained on the transit chord. By analyzing the timings of the anomalies we find the sky-projected stellar obliquity to be {lambda} = -1{sup +14}{sub -12} degrees. This result is consistent with (and more constraining than) a recent observation of the Rossiter-McLaughlin effect. It suggests that the planet migration mechanism preserved the initially low obliquity, or else that tidal evolution has realigned the system. Future applications of this method using data from the CoRoT and Kepler missions will allow spin-orbit alignment to be probed for many other exoplanets.« less
Focal plane subsystem design and performance for atmospheric chemistry from geostationary orbit tropospheric emissions monitoring of pollution

NASA Astrophysics Data System (ADS)

Gilmore, A. S.; Philbrick, R. H.; Funderburg, J.

2017-09-01

Remote sensing of pollutants are enabled from a satellite in a geostationary orbit containing an imaging spectrometer encompassing the wavelength ranges of 290 - 490 nm and 540 - 740 nm. As the first of NASA's Earth Venture Instrument Program, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) program will utilize this instrument to measure hourly air quality over a large portion of North America. The focal plane subsystem (FPS) contains two custom designed and critically aligned full frame transfer charge coupled devices (active area: 1028 x 2048, 18 μm) within a focal plane array package designed for radiation tolerance and space charging rejection. In addition, the FPS contains custom distributed focal plane electronics that provide all necessary clocks and biases to the sensors, receives all analog data from the sensors and performs 14 bit analog to digital conversion for upstream processing. Finally, the FPS encompasses custom low noise cables connecting the focal plane array and associated electronics. This paper discusses the design and performance of this novel focal plane subsystem with particular emphasis on the optical performance achieved including alignment, quantum efficiency, and modulation transfer function.
Band structure and spin texture of Bi2Se3 3 d ferromagnetic metal interface

NASA Astrophysics Data System (ADS)

Zhang, Jia; Velev, Julian P.; Dang, Xiaoqian; Tsymbal, Evgeny Y.

2016-07-01

The spin-helical surface states in a three-dimensional topological insulator (TI), such as Bi2Se3 , are predicted to have superior efficiency in converting charge current into spin polarization. This property is said to be responsible for the giant spin-orbit torques observed in ferromagnetic metal/TI structures. In this work, using first-principles and model tight-binding calculations, we investigate the interface between the topological insulator Bi2Se3 and 3 d -transition ferromagnetic metals Ni and Co. We find that the difference in the work functions of the topological insulator and the ferromagnetic metals shift the topological surface states down about 0.5 eV below the Fermi energy where the hybridization of these surface states with the metal bands destroys their helical spin structure. The band alignment of Bi2Se3 and Ni (Co) places the Fermi energy far in the conduction band of bulk Bi2Se3 , where the spin of the carriers is aligned with the magnetization in the metal. Our results indicate that the topological surface states are unlikely to be responsible for the huge spin-orbit torque effect observed experimentally in these systems.
Blue-light digital communication in underwater environments utilizing orbital angular momentum

NASA Astrophysics Data System (ADS)

Baghdady, Joshua; Miller, Keith; Osler, Sean; Morgan, Kaitlyn; Li, Wenzhe; Johnson, Eric; Cochenour, Brandon

2016-05-01

Underwater optical communication has recently become the topic of much investigation as the demands for underwater data transmission have rapidly grown in recent years. The need for reliable, high-speed, secure underwater communication has turned increasingly to blue-light optical solutions. The blue-green visible wavelength window provides an attractive solution to the problem of underwater data transmission thanks to its low attenuation, where traditional RF solutions used in free-space communications collapse. Beginning with GaN laser diodes as the optical source, this work explores the encoding and transmission of digital data across underwater environments of varying turbidities. Given the challenges present in an underwater environment, such as the mechanical and optical turbulences that make proper alignment difficult to maintain, it is desirable to achieve extremely high data rates in order to allow the time window of alignment between the transmitter and receiver to be as small as possible. In this paper, work is done to increase underwater data rates through the use of orbital angular momentum. Results are shown for a range of data rates across a variety of channel types ranging in turbidity from that of a clear ocean to a dirty harbor.
On-Orbit Multi-Field Wavefront Control with a Kalman Filter

NASA Technical Reports Server (NTRS)

Lou, John; Sigrist, Norbert; Basinger, Scott; Redding, David

2008-01-01

A document describes a multi-field wavefront control (WFC) procedure for the James Webb Space Telescope (JWST) on-orbit optical telescope element (OTE) fine-phasing using wavefront measurements at the NIRCam pupil. The control is applied to JWST primary mirror (PM) segments and secondary mirror (SM) simultaneously with a carefully selected ordering. Through computer simulations, the multi-field WFC procedure shows that it can reduce the initial system wavefront error (WFE), as caused by random initial system misalignments within the JWST fine-phasing error budget, from a few dozen micrometers to below 50 nm across the entire NIRCam Field of View, and the WFC procedure is also computationally stable as the Monte-Carlo simulations indicate. With the incorporation of a Kalman Filter (KF) as an optical state estimator into the WFC process, the robustness of the JWST OTE alignment process can be further improved. In the presence of some large optical misalignments, the Kalman state estimator can provide a reasonable estimate of the optical state, especially for those degrees of freedom that have a significant impact on the system WFE. The state estimate allows for a few corrections to the optical state to push the system towards its nominal state, and the result is that a large part of the WFE can be eliminated in this step. When the multi-field WFC procedure is applied after Kalman state estimate and correction, the stability of fine-phasing control is much more certain. Kalman Filter has been successfully applied to diverse applications as a robust and optimal state estimator. In the context of space-based optical system alignment based on wavefront measurements, a KF state estimator can combine all available wavefront measurements, past and present, as well as measurement and actuation error statistics to generate a Maximum-Likelihood optimal state estimator. The strength and flexibility of the KF algorithm make it attractive for use in real-time optical system alignment when WFC alone cannot effectively align the system.
Projector Augmented Wave formulation of orbital-dependent exchange-correlation functionals

NASA Astrophysics Data System (ADS)

Xu, Xiao; Holzwarth, N. A. W.

2012-02-01

The use of orbital-dependent exchange-correlation functionals within electronic structure calculations has recently received renewed attention for improving the accuracy of the calculations, especially correcting self-interaction errors. Since the Projector Augmented Wave (PAW) methodootnotetext P. Bl"ochl, Phys. Rev. B 50, 17953 (1994). is an efficient pseudopotential-like scheme which ensures accurate evaluation of all multipole moments of direct and exchange Coulomb integrals, it is a natural choice for implementing orbital-dependent formalisms. Using Fock exchange as an example of an orbital-dependent functional, we developed the formulation and numerical implementation of the approximate optimized effective potential formalism of Kreiger, Li, and Iafrate (KLI)ootnotetext J. B. Krieger, Y. Li, and G. J. Iafrate Phys. Rev. A 45, 101 (1992). within the PAW method, comparing results with the analogous Hartree-Fock treatment.ootnotetext Xiao Xu and N. A. W. Holzwarth, Phys. Rev. B 81, 245105 (2010); 84, 155113 (2011). Test results are presented for ground state properties of two well-known materials -- diamond and LiF. This formalism can be extended to treat orbital-dependent functionals more generally.

Orbital dependent functionals: An atom projector augmented wave method implementation

NASA Astrophysics Data System (ADS)

Xu, Xiao

This thesis explores the formulation and numerical implementation of orbital dependent exchange-correlation functionals within electronic structure calculations. These orbital-dependent exchange-correlation functionals have recently received renewed attention as a means to improve the physical representation of electron interactions within electronic structure calculations. In particular, electron self-interaction terms can be avoided. In this thesis, an orbital-dependent functional is considered in the context of Hartree-Fock (HF) theory as well as the Optimized Effective Potential (OEP) method and the approximate OEP method developed by Krieger, Li, and Iafrate, known as the KLI approximation. In this thesis, the Fock exchange term is used as a simple well-defined example of an orbital-dependent functional. The Projected Augmented Wave (PAW) method developed by P. E. Blochl has proven to be accurate and efficient for electronic structure calculations for local and semi-local functions because of its accurate evaluation of interaction integrals by controlling multiple moments. We have extended the PAW method to treat orbital-dependent functionals in Hartree-Fock theory and the Optimized Effective Potential method, particularly in the KLI approximation. In the course of study we develop a frozen-core orbital approximation that accurately treats the core electron contributions for above three methods. The main part of the thesis focuses on the treatment of spherical atoms. We have investigated the behavior of PAW-Hartree Fock and PAW-KLI basis, projector, and pseudopotential functions for several elements throughout the periodic table. We have also extended the formalism to the treatment of solids in a plane wave basis and implemented PWPAW-KLI code, which will appear in future publications.
COACH: profile-profile alignment of protein families using hidden Markov models.

PubMed

Edgar, Robert C; Sjölander, Kimmen

2004-05-22

Alignments of two multiple-sequence alignments, or statistical models of such alignments (profiles), have important applications in computational biology. The increased amount of information in a profile versus a single sequence can lead to more accurate alignments and more sensitive homolog detection in database searches. Several profile-profile alignment methods have been proposed and have been shown to improve sensitivity and alignment quality compared with sequence-sequence methods (such as BLAST) and profile-sequence methods (e.g. PSI-BLAST). Here we present a new approach to profile-profile alignment we call Comparison of Alignments by Constructing Hidden Markov Models (HMMs) (COACH). COACH aligns two multiple sequence alignments by constructing a profile HMM from one alignment and aligning the other to that HMM. We compare the alignment accuracy of COACH with two recently published methods: Yona and Levitt's prof_sim and Sadreyev and Grishin's COMPASS. On two sets of reference alignments selected from the FSSP database, we find that COACH is able, on average, to produce alignments giving the best coverage or the fewest errors, depending on the chosen parameter settings. COACH is freely available from www.drive5.com/lobster
Evolutionary distances in the twilight zone--a rational kernel approach.

PubMed

Schwarz, Roland F; Fletcher, William; Förster, Frank; Merget, Benjamin; Wolf, Matthias; Schultz, Jörg; Markowetz, Florian

2010-12-31

Phylogenetic tree reconstruction is traditionally based on multiple sequence alignments (MSAs) and heavily depends on the validity of this information bottleneck. With increasing sequence divergence, the quality of MSAs decays quickly. Alignment-free methods, on the other hand, are based on abstract string comparisons and avoid potential alignment problems. However, in general they are not biologically motivated and ignore our knowledge about the evolution of sequences. Thus, it is still a major open question how to define an evolutionary distance metric between divergent sequences that makes use of indel information and known substitution models without the need for a multiple alignment. Here we propose a new evolutionary distance metric to close this gap. It uses finite-state transducers to create a biologically motivated similarity score which models substitutions and indels, and does not depend on a multiple sequence alignment. The sequence similarity score is defined in analogy to pairwise alignments and additionally has the positive semi-definite property. We describe its derivation and show in simulation studies and real-world examples that it is more accurate in reconstructing phylogenies than competing methods. The result is a new and accurate way of determining evolutionary distances in and beyond the twilight zone of sequence alignments that is suitable for large datasets.
Distribution of tunnelling times for quantum electron transport.

PubMed

Rudge, Samuel L; Kosov, Daniel S

2016-03-28

In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.
Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

PubMed Central

Giorgioni, Anna; Paleari, Stefano; Cecchi, Stefano; Vitiello, Elisa; Grilli, Emanuele; Isella, Giovanni; Jantsch, Wolfgang; Fanciulli, Marco; Pezzoli, Fabio

2016-01-01

Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics. PMID:28000670
Manipulating the dipole layer of polar organic molecules on metal surfaces via different charge-transfer channels

NASA Astrophysics Data System (ADS)

Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Wang, Chin-Yung; Pi, Tun-Wen; Ishii, Hisao; Tang, S.-J.

The key properties of organic films such as energy level alignment (ELA), work functions, and injection barriers are closely linked to this dipole layer. Using angle resolved photoemission spectroscopy (ARPES), we systemically investigate the coverage-dependent work functions and spectra line shapes of occupied molecular orbital states of a polar molecule, chloroaluminium phthalocyanine (ClAlPc), grown on Ag(111) to show that the orientations of the first ClAlPc layer can be manipulated via the molecule deposition rate and post annealing, causing ELA at organic-metal interface to differ for about 0.3 eV between Cl-up and Cl-down configuration. Moreover, by comparing the experimental results with the calculations based on both gas-phase model and realistic model of ClAlPc on Ag(111) , we evidence that the different orientations of ClAlPc dipole layers lead to different charge-transfer channels between ClAlPc and Ag, a key factor that controls the ELA at organic-metal interface.
Spin-Filtering Rectifying and Negative Differential Resistance Behaviors in Co(dmit)2 Molecular Devices with Monatomic (C, Fe, Au) Electrodes

NASA Astrophysics Data System (ADS)

Yan, Shenlang; Long, Mengqiu; Zhang, Xiaojiao; He, Jun; Xu, Hui; Gao, Yongli

2014-09-01

Using nonequilibrium Green's functions (NEGFs) combined with the density functional theory (DFT), we study the electronic transport properties of a single molecule magnet Co(dmit)2, which is sandwiched between two monatomic chain electrodes, and the different electrode materials carbon, iron and gold, have been considered. The results show that the electrodes play a crucial role in the spin-dependent transport of the Co(dmit)2 molecular device, and some interesting phenomenon, such as perfect spin-filtering effect, rectifying and negative differential resistance (NDR) can be observed. We demonstrated that the magnetic Fe electrode can lead to high spin-flittering effect, and the different hybridization and alignment of energy levels between the molecule and the electrodes may be responsible for the rectification performance, and the distributions (delocalization or localization) of the frontier molecular orbitals under different bias result in the NDR behaviors. These characteristics could be used in the study of spin physics and the realization of nanospintronic devices.
Astrometric confirmation and preliminary orbital parameters of the young exoplanet 51 Eridani b with the Gemini Planet Imager

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Rosa, Robert J.; Nielsen, Eric L.; Blunt, Sarah C.

We present new Gemini Planet Imager observations of the young exoplanet 51 Eridani b that provide further evidence that the companion is physically associated with 51 Eridani. Combining this new astrometric measurement with those reported in the literature, we significantly reduce the posterior probability that 51 Eridani b is an unbound foreground or background T-dwarf in a chance alignment with 51 Eridani to 2 × 10 –7, an order of magnitude lower than previously reported. If 51 Eridani b is indeed a bound object, then we have detected orbital motion of the planet between the discovery epoch and the latest epoch. By implementing a computationally efficient Monte Carlo technique, preliminary constraints are placed on the orbital parameters of the system. The current set of astrometric measurements suggest an orbital semimajor axis ofmore » $${14}_{-3}^{+7}$$ AU, corresponding to a period of $${41}_{-12}^{+35}$$ years (assuming a mass of 1.75 M⊙ for the central star), and an inclination of $${138}_{-13}^{+15}$$ deg. The remaining orbital elements are only marginally constrained by the current measurements. As a result, these preliminary values suggest an orbit that does not share the same inclination as the orbit of the distant M-dwarf binary, GJ 3305, which is a wide physically bound companion to 51 Eridani.« less
Astrometric confirmation and preliminary orbital parameters of the young exoplanet 51 Eridani b with the Gemini Planet Imager

DOE PAGES

De Rosa, Robert J.; Nielsen, Eric L.; Blunt, Sarah C.; ...

2015-11-13

We present new Gemini Planet Imager observations of the young exoplanet 51 Eridani b that provide further evidence that the companion is physically associated with 51 Eridani. Combining this new astrometric measurement with those reported in the literature, we significantly reduce the posterior probability that 51 Eridani b is an unbound foreground or background T-dwarf in a chance alignment with 51 Eridani to 2 × 10 –7, an order of magnitude lower than previously reported. If 51 Eridani b is indeed a bound object, then we have detected orbital motion of the planet between the discovery epoch and the latest epoch. By implementing a computationally efficient Monte Carlo technique, preliminary constraints are placed on the orbital parameters of the system. The current set of astrometric measurements suggest an orbital semimajor axis ofmore » $${14}_{-3}^{+7}$$ AU, corresponding to a period of $${41}_{-12}^{+35}$$ years (assuming a mass of 1.75 M⊙ for the central star), and an inclination of $${138}_{-13}^{+15}$$ deg. The remaining orbital elements are only marginally constrained by the current measurements. As a result, these preliminary values suggest an orbit that does not share the same inclination as the orbit of the distant M-dwarf binary, GJ 3305, which is a wide physically bound companion to 51 Eridani.« less
Ferroelectric switching of band alignments in LSMO/PZT/Co multiferroic tunnel junctions: an ab initio study.

PubMed

Imam, M; Stojić, N; Binggeli, N

2017-08-04

Band alignments in ferroelectric tunnel junctions (FTJs) are expected to play a critical role in determining the charge transport across the tunneling barrier. In general, however, the interface band discontinuities and their polarization dependence are not well known in these systems. Using a first-principles density-functional-theory approach, we explore the ferroelectric (FE) polarization dependence of the band alignments in [Formula: see text] (LSMO/PZT/Co) multiferroic tunnel junctions, for which recent experiments indicated an ON/OFF conductivity behavior upon switching the PZT FE polarization. Our results on the pseudomorphic defect-free LSMO/PZT/Co FTJs evidence a major FE switching effect on the band discontinuities at both interfaces. Based on the changes in the band alignments, we provide a possible explanation for the observed trends in the resistive switching.
Vibrational and rotational sequences in 101Mo and 103,4Ru studied via multinucleon transfer reactions

DOE PAGES

Regan, P. H.; Wheldon, C.; Yamamoto, A. D.; ...

2005-04-01

The near-yrast states of 42 101Mo 59 and 44 103,4Ru 59,60 have been studied following their population via heavy-ion multinucleon transfer reactions between a 136 Xe beam and a thin, self-supporting 100Mo target. The ground state sequence in 104Ru can be understood as demonstrating a simple evolution from a quasi-vibrational structure at lower spins to statically deformed, quasi-rotational excitation involving the population of a pair of low-Ω h 11/2 neutron orbitals. The effect of the decoupled h 11/2 orbital on this vibration-to-rotational evolution is demonstrated by an extension of the "E-GOS" prescription to include odd-A nuclei. The experimental results aremore » also compared with self-consistent Total Routhian Surface calculations which also highlight the polarising role of the highly aligned neutron h 11/2 orbital in these nuclei.« less
Lattice Commissioning Stretgy Simulation for the B Factory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, M.; Whittum, D.; Yan, Y.

2011-08-26

To prepare for the PEP-II turn on, we have studied one commissioning strategy with simulated lattice errors. Features such as difference and absolute orbit analysis and correction are discussed. To prepare for the commissioning of the PEP-II injection line and high energy ring (HER), we have developed a system for on-line orbit analysis by merging two existing codes: LEGO and RESOLVE. With the LEGO-RESOLVE system, we can study the problem of finding quadrupole alignment and beam position (BPM) offset errors with simulated data. We have increased the speed and versatility of the orbit analysis process by using a command filemore » written in a script language designed specifically for RESOLVE. In addition, we have interfaced the LEGO-RESOLVE system to the control system of the B-Factory. In this paper, we describe online analysis features of the LEGO-RESOLVE system and present examples of practical applications.« less
The CAMEO barium release - E/parallel/ fields over the polar cap

NASA Technical Reports Server (NTRS)

Heppner, J. P.; Miller, M. L.; Pongratz, M. B.; Smith, G. M.; Smith, L. L.; Mende, S. B.; Nath, N. R.

1981-01-01

Four successive thermite barium releases at an altitude of 965 km over polar cap invariant latitudes 84 to 76 deg near magnetic midnight were conducted from the orbiting second stage of the vehicle that launched Nimbus 7; the releases were made as part of the CAMEO (Chemically Active Material Ejected in Orbit) program. This was the first opportunity to observe the behavior of conventional barium release when conducted at orbital velocity in the near-earth magnetic field. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba(+) expansion velocity relative to an expected velocity of 0.9 km/s. Attention is also given to neutral cloud expansion, initial ion cloud expansion, convective motion, and the characteristics of field-aligned motion. The possibility of measuring parallel electric fields over the polar cap by observing perturbations in the motion of the visible ions is assessed.
The on-orbit calibration of the Fermi Large Area Telescope

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2009-09-06

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here in this work, we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be describedmore » in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. Lastly, these results have been used to calibrate the LAT datasets to be publicly released in August 2009.« less
Double-lunar swingby trajectories for the spacecraft of the International Solar Terrestrial Physics program

NASA Technical Reports Server (NTRS)

Dunham, David W.; Jen, Shao-Chiang; Lee, Taesul; Swade, D.; Kawaguchi, Jun'ichiro; Farquhar, Robert W.; Broaddus, S.; Engel, Cheryl

1989-01-01

The ISEE-3 satellite carried out the first extensive exploration of the distant geomagnetic tail during 1983. ISEE-3's orbit was altered with four lunar gravity assists that alternately decreased and increased its orbital energy while keeping the apogees aligned in the antisolar direction. Two spacecraft of the International Solar Terrestrial Physics program will use similar double-lunar swingby orbits to study the solar wind and the geomagnetic environment. Geotail will be built in Japan for the Institute of Space and Astronautical Sciences; its main purpose will be to explore the earth's geomagnetic tail. Wind is a NASA spacecraft that will monitor the solar wind upstream from the earth and will also study the bowshock region of the magnetosphere. Current plans call for launches of both by NASA with expendable launch vehicles during the second half of 1992.
Diffractive optics for precision alignment of Euclid space telescope optics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Asfour, Jean-Michel; Weidner, Frank; Bodendorf, Christof; Bode, Andreas; Poleshchuk, Alexander G.; Nasyrov, Ruslan K.; Grupp, Frank; Bender, Ralf

2017-09-01

We present a method for precise alignment of lens elements using specific Computer Generated Hologram (CGH) with an integrated Fizeau reference flat surface and a Fizeau interferometer. The method is used for aligning the so called Camera Lens Assembly for ESAs Euclid telescope. Each lens has a corresponding annular area on the diffractive optics, which is used to control the position of each lens. The lenses are subsequently positioned using individual annular rings of the CGH. The overall alignment accuracy is below 1 µm, the alignment sensitivity is in the range of 0.1 µm. The achieved alignment accuracy of the lenses relative to each other is mainly depending on the stability in time of the alignment tower. Error budgets when using computer generated holograms and physical limitations are explained. Calibration measurements of the alignment system and the typically reached alignment accuracies will be shown and discussed.
Pupil Alignment Considerations for Large, Deployable Space Telescopes

NASA Technical Reports Server (NTRS)

Bos, Brent J.; Ohl, Raymond G.; Kubalak, Daivd A.

2011-01-01

For many optical systems the properties and alignment of the internal apertures and pupils are not critical or controlled with high precision during optical system design, fabrication or assembly. In wide angle imaging systems, for instance, the entrance pupil position and orientation is typically unconstrained and varies over the system s field of view in order to optimize image quality. Aperture tolerances usually do not receive the same amount of scrutiny as optical surface aberrations or throughput characteristics because performance degradation is typically graceful with misalignment, generally only causing a slight reduction in system sensitivity due to vignetting. But for a large deployable space-based observatory like the James Webb Space Telescope (JWST), we have found that pupil alignment is a key parameter. For in addition to vignetting, JWST pupil errors cause uncertainty in the wavefront sensing process that is used to construct the observatory on-orbit. Furthermore they also open stray light paths that degrade the science return from some of the telescope s instrument channels. In response to these consequences, we have developed several pupil measurement techniques for the cryogenic vacuum test where JWST science instrument pupil alignment is verified. These approaches use pupil alignment references within the JWST science instruments; pupil imaging lenses in three science instrument channels; and unique pupil characterization features in the optical test equipment. This will allow us to verify and crosscheck the lateral pupil alignment of the JWST science instruments to approximately 1-2% of their pupil diameters.
Constraining the Absolute Orientation of eta Carinae's Binary Orbit: A 3-D Dynamical Model for the Broad [Fe III] Emission

NASA Technical Reports Server (NTRS)

Madura, T. I.; Gull, T. R.; Owocki, S. P.; Groh, J. H.; Okazaki, A. T.; Russell, C. M. P.

2011-01-01

We present a three-dimensional (3-D) dynamical model for the broad [Fe III] emission observed in Eta Carinae using the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS). This model is based on full 3-D Smoothed Particle Hydrodynamics (SPH) simulations of Eta Car's binary colliding winds. Radiative transfer codes are used to generate synthetic spectro-images of [Fe III] emission line structures at various observed orbital phases and STIS slit position angles (PAs). Through a parameter study that varies the orbital inclination i, the PA(theta) that the orbital plane projection of the line-of-sight makes with the apastron side of the semi-major axis, and the PA on the sky of the orbital axis, we are able, for the first time, to tightly constrain the absolute 3-D orientation of the binary orbit. To simultaneously reproduce the blue-shifted emission arcs observed at orbital phase 0.976, STIS slit PA = +38deg, and the temporal variations in emission seen at negative slit PAs, the binary needs to have an i approx. = 130deg to 145deg, Theta approx. = -15deg to +30deg, and an orbital axis projected on the sky at a P A approx. = 302deg to 327deg east of north. This represents a system with an orbital axis that is closely aligned with the inferred polar axis of the Homunculus nebula, in 3-D. The companion star, Eta(sub B), thus orbits clockwise on the sky and is on the observer's side of the system at apastron. This orientation has important implications for theories for the formation of the Homunculus and helps lay the groundwork for orbital modeling to determine the stellar masses.
Orbital shape in intentional skull deformations and adult sagittal craniosynostoses.

PubMed

Sandy, Ronak; Hennocq, Quentin; Nysjö, Johan; Giran, Guillaume; Friess, Martin; Khonsari, Roman Hossein

2018-06-21

Intentional cranial deformations are the result of external mechanical forces exerted on the skull vault that modify the morphology of various craniofacial structures such as the skull base, the orbits and the zygoma. In this controlled study, we investigated the 3D shape of the orbital inner mould and the orbital volume in various types of intentional deformations and in adult non-operated scaphocephaly - the most common type of craniosynostosis - using dedicated morphometric methods. CT scans were performed on 32 adult skulls with intentional deformations, 21 adult skull with scaphocephaly and 17 non-deformed adult skulls from the collections of the Muséum national d'Histoire naturelle in Paris, France. The intentional deformations group included six skulls with Toulouse deformations, eight skulls with circumferential deformations and 18 skulls with antero-posterior deformations. Mean shape models were generated based on a semi-automatic segmentation technique. Orbits were then aligned and compared qualitatively and quantitatively using colour-coded distance maps and by computing the mean absolute distance, the Hausdorff distance, and the Dice similarity coefficient. Orbital symmetry was assessed after mirroring, superimposition and Dice similarity coefficient computation. We showed that orbital shapes were significantly and symmetrically modified in intentional deformations and scaphocephaly compared with non-deformed control skulls. Antero-posterior and circumferential deformations demonstrated a similar and severe orbital deformation pattern resulting in significant smaller orbital volumes. Scaphocephaly and Toulouse deformations had similar deformation patterns but had no effect on orbital volumes. This study showed that intentional deformations and scaphocephaly significantly interact with orbital growth. Our approach was nevertheless not sufficient to identify specific modifications caused by the different types of skull deformations or by scaphocephaly. © 2018 Anatomical Society.
The Search for Planet Nine

NASA Astrophysics Data System (ADS)

Brown, Michael E.; Batygin, Konstantin

2016-10-01

We use an extensive suite of numerical simulations to constrain the mass and orbit of Planet Nine, and we use these constraints to begin the search for this newly proposed planet in new and in archival data. Here, we compare our simulations to the observed population of aligned eccentric high semimajor axis Kuiper belt objects and determine which simulation parameters are statistically compatible with the observations. We find that only a narrow range of orbital elements can reproduce the observations. In particular, the combination of semimajor axis, eccentricity, and mass of Planet Nine strongly dictates the semimajor axis range of the orbital confinement of the distant eccentric Kuiper belt objects. Allowed orbits, which confine Kuiper belt objects with semimajor axis beyond 380 AU, have perihelia roughly between 150 and 350 AU, semimajor axes between 380 and 980 AU, and masses between 5 and 20 Earth masses. Orbitally confined objects also generally have orbital planes similar to that of the planet, suggesting that the planet is inclined approximately 30 degrees to the ecliptic. We compare the allowed orbital positions and estimated brightness of Planet Nine to previous and ongoing surveys which would be sensitive to the planet's detection and use these surveys to rule out approximately two-thirds of the planet's orbit. Planet Nine is likely near aphelion with an approximate brightness of 22

Space Technology 5 Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, G.; Wang, Y.; Slavin, J. A.; Strangeway, R. L.

2009-01-01

Space Technology 5 (ST5) is a constellation mission consisting of three microsatellites. It provides the first multipoint magnetic field measurements in low Earth orbit, which enables us to separate spatial and temporal variations. In this paper, we present a study of the temporal variability of field-aligned currents using the ST5 data. We examine the field-aligned current observations during and after a geomagnetic storm and compare the magnetic field profiles at the three spacecraft. The multipoint data demonstrate that mesoscale current structures, commonly embedded within large-scale current sheets, are very dynamic with highly variable current density and/or polarity in approx.10 min time scales. On the other hand, the data also show that the time scales for the currents to be relatively stable are approx.1 min for mesoscale currents and approx.10 min for large-scale currents. These temporal features are very likely associated with dynamic variations of their charge carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of mesoscale field-aligned currents are found to be consistent with those of auroral parallel electric field.
DFT investigation on the electronic structure of Faujasite

NASA Astrophysics Data System (ADS)

Popeneciu, Horea; Calborean, Adrian; Tudoran, Cristian; Buimaga-Iarinca, Luiza

2013-11-01

We report here first-principle pseudopotential DFT calculations to investigate relevant aspects of the electronic structure of zeolites based FAU. Fundamental molecular issues of the band-gap and electronic population analysis were reviewed under GGA/RPBE level of theory, corroborated with a DZP basis set and Troullier-Martins norm conserving pseudo-potentials. The atom-projected density of states and the analysis of HOMO-LUMO frontier orbitals at Gamma point were performed. Their electronic transfers are discussed through the alignment and relative positions of orbitals in order to determine the way that the molecule interacts with adsorbed molecules and other practical applications. Mulliken population analysis was employed for describing atomic charge distribution in the chosen systems.
Influence of coherent mesoscale structures on satellite-based Doppler lidar wind measurements

NASA Technical Reports Server (NTRS)

Emmitt, G. D.; Houston, S.

1985-01-01

Efforts to develop display routines for overlaying gridded and nongridded data sets are discussed. The primary objective is to have the capability to review global patterns of winds and lidar samples; to zoom in on particular wind features or global areas; and to display contours of wind components and derived fields (e.g., divergence, vorticity, deformation, etc.). Current considerations in support of a polar orbiting shuttle lidar mission are discussed. Ground truth for a shuttle lidar experiment may be limited to fortuitous alignment of lidar wind profiles and scheduled rawinsonde profiles. Any improvement on this would require special rawinsonde launches and/or optimization of the shuttle orbit with global wind measurement networks.
Quantum Monte Carlo for the x-ray absorption spectrum of pyrrole at the nitrogen K-edge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zubarev, Dmitry Yu.; Austin, Brian M.; Lester, William A. Jr.

Fixed-node diffusion Monte Carlo (FNDMC) is used to simulate the x-ray absorption spectrum of a gas-phase pyrrole molecule at the nitrogen K-edge. Trial wave functions for core-excited states are constructed from ground-state Kohn-Sham determinants substituted with singly occupied natural orbitals from configuration interaction with single excitations calculations of the five lowest valence-excited triplet states. The FNDMC ionization potential (IP) is found to lie within 0.3 eV of the experimental value of 406.1 {+-} 0.1 eV. The transition energies to anti-bonding virtual orbitals match the experimental spectrum after alignment of IP values and agree with the existing assignments.
Robust through-the-wall radar image classification using a target-model alignment procedure.

PubMed

Smith, Graeme E; Mobasseri, Bijan G

2012-02-01

A through-the-wall radar image (TWRI) bears little resemblance to the equivalent optical image, making it difficult to interpret. To maximize the intelligence that may be obtained, it is desirable to automate the classification of targets in the image to support human operators. This paper presents a technique for classifying stationary targets based on the high-range resolution profile (HRRP) extracted from 3-D TWRIs. The dependence of the image on the target location is discussed using a system point spread function (PSF) approach. It is shown that the position dependence will cause a classifier to fail, unless the image to be classified is aligned to a classifier-training location. A target image alignment technique based on deconvolution of the image with the system PSF is proposed. Comparison of the aligned target images with measured images shows the alignment process introducing normalized mean squared error (NMSE) ≤ 9%. The HRRP extracted from aligned target images are classified using a naive Bayesian classifier supported by principal component analysis. The classifier is tested using a real TWRI of canonical targets behind a concrete wall and shown to obtain correct classification rates ≥ 97%. © 2011 IEEE
Long Term Missions at the Sun-Earth Libration Point L1: ACE, SOHO, and WIND

NASA Technical Reports Server (NTRS)

Roberts, Craig E.

2011-01-01

Three heliophysics missions -- the Advanced Composition Explorer (ACE), Solar Heliospheric Observatory (SOHO), and the Global Geoscience WIND -- have been orbiting the Sun-Earth interior libration point L1 continuously since 1997, 1996, and 2004, respectively. ACE and WIND (both NASA missions) and SOHO (an ESA-NASA joint mission) are all operated from the NASA Goddard Space Flight Center (GSFC). While ACE and SOHO have been dedicated libration point orbiters since their launches, WIND has had also a remarkable 10-year career flying a deep-space, multiple lunar-flyby trajectory prior to 2004. That era featured 36 targeted lunar flybys with excursions to both L1 and L2 before its final insertion in L1 orbit. A figure depicts the orbits of the three spacecraft, showing projections of the orbits onto the orthographic planes of a solar rotating ecliptic frame of reference. The SOHO orbit is a quasi-periodic halo orbit, where the frequencies of the in-plane and out-of-plane motions are practically equal. Such an orbit is seen to repeat itself with a period of approximately 178 days. For ACE and WIND, the frequencies of the in-plane and out-of-plane motions are unequal, giving rise to the characteristic Lissajous motion. ACE's orbit is of moderately small amplitude, whereas WIND's orbit is a large-amplitude Lissajous of dimensions close to those of the SOHO halo orbit. As motion about the collinear points is inherently unstable, stationkeeping maneuvers are necessary to prevent orbital decay and eventual escape from the L1 region. Though the three spacecraft are dissimilar (SOHO is a 3-axis stabilized Sun pointer, WIND is a spin-stabilized ecliptic pole pointer, and ACE is also spin-stabilized with its spin axis maintained between 4 and 20 degrees of the Sun), the stationkeeping technique for the three is fundamentally the same. The technique consists of correcting the energy of the orbit via a delta-V directed parallel or anti-parallel to the Spacecraft-to-Sun line. SOHO achieves this using thrusters oriented in line with the solar direction. WIND achieves the delta-V via pulsing radial thrusters when aligned with the Sun. ACE uses axial thrusters to apply delta-V with a component that is 94% or more aligned with the ACE-Sun line. Sunward thrust adds energy to the orbit preventing decay back toward Earth. Thrust directed anti-Sunward takes energy out of the L1 orbit, thereby preventing escape from the Earth-Moon system into independent heliocentric orbit. Libration point orbit stationkeeping delta-V costs grow exponentially with time elapsed from the last maneuver performed. The doubling time constant is approximately 16 days. For the sake of fuel conservation, and for limiting the absolute magnitude of propulsion performance errors, stationkeeping maneuvers should be performed before the delta-V grows too large; for our purposes 'too large' is considered to be greater than 0.5 m/sec. In practice, the typical interval between burns for this trio is about three months, and the typical delta-V is much smaller than 0.5 m/sec. Typical annual stationkeeping costs have been around 1.0 m/sec for ACE and WIND, and much less than that for SOHO. All three spacecraft have ample fuel remaining; barring contingencies all three could, in principle, be maintained at L1 for decades to come. This paper will review the L1 orbits and the mission history of ACE, WIND, and SOHO, and describe the stationkeeping techniques and orbit maneuver experience. The Lissajous phase control that was practiced for ACE during the period from 1999 to 2001 will also be briefly discussed. The final section will consider the future of these ongoing missions.
Resilience of hybrid optical angular momentum qubits to turbulence

PubMed Central

Farías, Osvaldo Jiménez; D'Ambrosio, Vincenzo; Taballione, Caterina; Bisesto, Fabrizio; Slussarenko, Sergei; Aolita, Leandro; Marrucci, Lorenzo; Walborn, Stephen P.; Sciarrino, Fabio

2015-01-01

Recent schemes to encode quantum information into the total angular momentum of light, defining rotation-invariant hybrid qubits composed of the polarization and orbital angular momentum degrees of freedom, present interesting applications for quantum information technology. However, there remains the question as to how detrimental effects such as random spatial perturbations affect these encodings. Here, we demonstrate that alignment-free quantum communication through a turbulent channel based on hybrid qubits can be achieved with unit transmission fidelity. In our experiment, alignment-free qubits are produced with q-plates and sent through a homemade turbulence chamber. The decoding procedure, also realized with q-plates, relies on both degrees of freedom and renders an intrinsic error-filtering mechanism that maps errors into losses. PMID:25672667
Efficient Charge Transfer and Fine-Tuned Energy Level Alignment in a THF-Processed Fullerene-Free Organic Solar Cell with 11.3% Efficiency.

PubMed

Zheng, Zhong; Awartani, Omar M; Gautam, Bhoj; Liu, Delong; Qin, Yunpeng; Li, Wanning; Bataller, Alexander; Gundogdu, Kenan; Ade, Harald; Hou, Jianhui

2017-02-01

Fullerene-free organic solar cells show over 11% power conversion efficiency, processed by low toxic solvents. The applied donor and acceptor in the bulk heterojunction exhibit almost the same highest occupied molecular orbital level, yet exhibit very efficient charge creation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Development of a high stability pointing mechanism for wide application

NASA Technical Reports Server (NTRS)

Brunnen, A. J. D.; Bentall, R. H.

1982-01-01

A recurrent requirement of spaceborne instruments and communications equipment is that of accurate pointing. This need is recognizable in such diverse applications as Star Sensor trimming, Momentum Wheel gimballing, in-orbit adjustment or alignment of equipment, inter-satellite communication and Antenna Pointing. A pointing mechanism of novel design having several advantages over the more conventional gimbal, centre-pivoted, or cross axis pointing concepts is described.
Evaluation of the thin deformable active optics mirror concept

NASA Technical Reports Server (NTRS)

Robertson, H. J.

1972-01-01

The active optics concept using a thin deformable mirror has been successfully demonstrated using a 30 in. diameter, 1/2 in. thick mirror and a 61 point matrix of forces for alignment. Many of the problems associated with the design, fabrication, and launch of large aperture diffraction-limited astronomical telescopes have been resolved and experimental data created that can provide accurate predictions of performance in orbit.
Scale dependence of the alignment between strain rate and rotation in turbulent shear flow

NASA Astrophysics Data System (ADS)

Fiscaletti, D.; Elsinga, G. E.; Attili, A.; Bisetti, F.; Buxton, O. R. H.

2016-10-01

The scale dependence of the statistical alignment tendencies of the eigenvectors of the strain-rate tensor ei, with the vorticity vector ω , is examined in the self-preserving region of a planar turbulent mixing layer. Data from a direct numerical simulation are filtered at various length scales and the probability density functions of the magnitude of the alignment cosines between the two unit vectors | ei.ω ̂| are examined. It is observed that the alignment tendencies are insensitive to the concurrent large-scale velocity fluctuations, but are quantitatively affected by the nature of the concurrent large-scale velocity-gradient fluctuations. It is confirmed that the small-scale (local) vorticity vector is preferentially aligned in parallel with the large-scale (background) extensive strain-rate eigenvector e1, in contrast to the global tendency for ω to be aligned in parallel with the intermediate strain-rate eigenvector [Hamlington et al., Phys. Fluids 20, 111703 (2008), 10.1063/1.3021055]. When only data from regions of the flow that exhibit strong swirling are included, the so-called high-enstrophy worms, the alignment tendencies are exaggerated with respect to the global picture. These findings support the notion that the production of enstrophy, responsible for a net cascade of turbulent kinetic energy from large scales to small scales, is driven by vorticity stretching due to the preferential parallel alignment between ω and nonlocal e1 and that the strongly swirling worms are kinematically significant to this process.
Induced charging of shuttle orbiter by high electron-beam currents

NASA Technical Reports Server (NTRS)

Liemohn, H. B.

1977-01-01

Emission of high-current electron beams that was proposed for some Spacelab payloads required substantial return currents to the orbiter skin in order to neutralize the beam charge. Since the outer skin of the vehicle was covered with approximately 1200 sq m of thermal insulation which has the dielectric quality of air and an electrical conductivity that was estimated by NASA at 10 to the -9 power to 10 to the -10 power mhos/m, considerable transient charging and local potential differences were anticipated across the insulation. The theory for induced charging of spacecraft due to operation of electron guns was only developed for spherical metal vehicles and constant emission currents, which were not directly applicable to the orbiter situation. Field-aligned collection of electron return current from the ambient ionosphere at orbiter altitudes provides up to approximately 150 mA on the conducting surfaces and approximately 2.4 A on the dielectric thermal insulation. Local ionization of the neutral atmosphere by energetic electron bombardment or electrical breakdown may provide somewhat more return current.
The behavior of cold gas in spheroidal galactic potentials

NASA Astrophysics Data System (ADS)

Simonson, G. F.

1982-03-01

The motions of cold gas residing in various spheroidal galactic potential wells are investigated, both analytically and through extensive numerical calculations. It is found that a gaseous layer embedded in the potential has a preferred orientation, in which individual gas clouds have orbits which do not precess. The gas will damp to the preferred orbits, through the combined effects of differential precession and radial excursions from circular trajectories, on time scales of less than one to two billion years for orbits of moderate radius. For elliptical galaxies with embedded gas disks this work provides a clear discriminator between prolate and oblate mass distributions. The preferred gas orbits lie in the equatorial planes of both of these potentials, so if a gas disk is seen projected against the minor axis of an elliptical, that galaxy is truly prolate, while if the lane is aligned with the major axis, the system is oblate. Tabulated observations show that both prolate and oblate ellipticals exist, in perhaps equal numbers. True axial ratios and spatial orientations can also be determined for these objects.
Afterbody Heating Characteristics of a Proposed Mars Sample Return Orbiter

NASA Technical Reports Server (NTRS)

Horvath, Thomas J.; Heiner, Nicholas C.; Olguin, Daniella M.; Cheatwood, F. McNeil; Gnoffo, Peter A.

2001-01-01

Aeroheating wind-tunnel tests were conducted on a 0.028 scale model of an orbiter concept considered for a possible Mars sample return mission. The primary experimental objectives were to characterize hypersonic near wake closure and determine if shear layer impingement would occur on the proposed orbiter afterbody at incidence angles necessary for a Martian aerocapture maneuver. Global heat transfer mappings, surface streamline patterns, and shock shapes were obtained in the NASA Langley 20-inch Mach 6 Air and CF4 Tunnels for post-normal shock Reynolds numbers (based on forebody diameter) ranging from 1,400 to 415,000, angles of attack ranging from -5 to 10 degrees at 0, 3, and 6 deg sideslip, and normal-shock density, ratios of 5 and 12. Laminar, transitional, and turbulent shear layer impingement on the cylindrical afterbody was inferred from the measurements and resulted in a localized heating maximum that ranged from 40 to 75% of the reference forebody stagnation point heating. Comparison of laminar heating prediction to experimental measurement along the orbiter afterbody highlight grid alignment challenges associated with numerical simulation of three-dimensional separated wake flows.
Operating Small Sat Swarms as a Single Entity: Introducing SODA

NASA Technical Reports Server (NTRS)

Conn, Tracie; Plice, Laura; Dono Perez, Andres; Ho, Michael

2017-01-01

NASA's decadal survey determined that simultaneous measurements from a 3D volume of space are advantageous for a variety of studies in space physics and Earth science. Therefore, swarm concepts with multiple spacecraft in close proximity are a growing topic of interest in the small satellite community. Among the capabilities needed for swarm missions is a means to maintain operator-specified geometry, alignment, or separation. Swarm stationkeeping poses a planning challenge due to the limited scalability of ground resources. To address scalable control of orbital dynamics, we introduce SODA - Swarm Orbital Dynamics Advisor - a tool that accepts high-level configuration commands and provides the orbital maneuvers needed to achieve the desired type of swarm relative motion. Rather than conventional path planning, SODA's innovation is the use of artificial potential functions to define boundaries and keepout regions. The software architecture includes high fidelity propagation, accommodates manual or automated inputs, displays motion animations, and returns maneuver commands and analytical results. Currently, two swarm types are enabled: in-train distribution and an ellipsoid volume container. Additional swarm types, simulation applications, and orbital destinations are in planning stages.
Theoretical study of spin Hall effect in conjugated Organic semiconductors

NASA Astrophysics Data System (ADS)

Mahani, M. R.; Delin, A.

The spin Hall effect (SHE), a direct conversion between electronic and spin currents, is a rapidly growing branch of spintronics. The study of SHE in conjugated polymers has gained momentum recently due to the weak spin-orbit couplings and hyperfine interactions in these materials. Our calculations of SHE based on the recent work, are the result of the misalignment of pi-orbitals in triads consisting of three molecules. In disordered organics, where the electronic conduction is through hopping of the electrons among randomly oriented molecules, instead of identifying a hopping triad to represent the entire system, we numerically solve the master equations for electrical and spin hall conductivities by summing the contributions from all triads in a sufficiently large system. The interference between the direct and indirect hoppings in these triads leads to SHE proportional to the orientation vector of molecule at the first order of spin-orbit coupling. Hence, our results show, the degree of molecular alignment as well as the strength of the spin-orbit coupling can be used to control the SHE in organics.
First evidence of anisotropy of GPS phase slips caused by the mid-latitude field-aligned ionospheric irregularities

NASA Astrophysics Data System (ADS)

Afraimovich, E. L.; Ishin, A. B.; Tinin, M. V.; Yasyukevich, Yu. V.; Jin, S. G.

2011-05-01

The mid-latitude field-aligned irregularity (FAI) along the magnetic field line is a common phenomenon in the ionosphere. However, few data reveal the field-aligned ionospheric irregularities. They are insufficient to identify FAIs effects so far, particularly effect on global positioning system (GPS) signals. In this paper, the mid-latitude FAIs by line-of-sight angular scanning relative to the local magnetic field vector are investigated using the denser GPS network observations in Japan. It has been the first found that total GPS L2 phase slips over Japan, during the recovery phase of the 12 Feb 2000 geomagnetic storm were caused by GPS signal scattering on FAIs both for the lines-of-sight aligned to the magnetic field line (the field of aligned scattering, FALS) and across the magnetic field line (the field of across scattering, FACS). The FALS results are also in a good agreement with the data of the magnetic field orientation control of GPS occultation observations of equatorial scintillation during thorough low earth orbit (LEO) satellites measurements, e.g. Challenging Minisatellite Payload (CHAMP) and Satellite de Aplicaciones Cientificas-C (SAC-C). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors.
Probability of coincidental similarity among the orbits of small bodies - I. Pairing

NASA Astrophysics Data System (ADS)

Jopek, Tadeusz Jan; Bronikowska, Małgorzata

2017-09-01

Probability of coincidental clustering among orbits of comets, asteroids and meteoroids depends on many factors like: the size of the orbital sample searched for clusters or the size of the identified group, it is different for groups of 2,3,4,… members. Probability of coincidental clustering is assessed by the numerical simulation, therefore, it depends also on the method used for the synthetic orbits generation. We have tested the impact of some of these factors. For a given size of the orbital sample we have assessed probability of random pairing among several orbital populations of different sizes. We have found how these probabilities vary with the size of the orbital samples. Finally, keeping fixed size of the orbital sample we have shown that the probability of random pairing can be significantly different for the orbital samples obtained by different observation techniques. Also for the user convenience we have obtained several formulae which, for given size of the orbital sample can be used to calculate the similarity threshold corresponding to the small value of the probability of coincidental similarity among two orbits.
Pulsed Accretion in the T Tauri Binary TWA 3A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tofflemire, Benjamin M.; Mathieu, Robert D.; Herczeg, Gregory J.

TWA 3A is the most recent addition to a small group of young binary systems that both actively accrete from a circumbinary disk and have spectroscopic orbital solutions. As such, it provides a unique opportunity to test binary accretion theory in a well-constrained setting. To examine TWA 3A’s time-variable accretion behavior, we have conducted a two-year, optical photometric monitoring campaign, obtaining dense orbital phase coverage (∼20 observations per orbit) for ∼15 orbital periods. From U -band measurements we derive the time-dependent binary mass accretion rate, finding bursts of accretion near each periastron passage. On average, these enhanced accretion events evolvemore » over orbital phases 0.85 to 1.05, reaching their peak at periastron. The specific accretion rate increases above the quiescent value by a factor of ∼4 on average but the peak can be as high as an order of magnitude in a given orbit. The phase dependence and amplitude of TWA 3A accretion is in good agreement with numerical simulations of binary accretion with similar orbital parameters. In these simulations, periastron accretion bursts are fueled by periodic streams of material from the circumbinary disk that are driven by the binary orbit. We find that TWA 3A’s average accretion behavior is remarkably similar to DQ Tau, another T Tauri binary with similar orbital parameters, but with significantly less variability from orbit to orbit. This is only the second clear case of orbital-phase-dependent accretion in a T Tauri binary.« less
Single-stage soft tissue reconstruction and orbital fracture repair for complex facial injuries.

PubMed

Wu, Peng Sen; Matoo, Reshvin; Sun, Hong; Song, Li Yuan; Kikkawa, Don O; Lu, Wei

2017-02-01

Orbital fractures with open periorbital wounds cause significant morbidity. Timing of debridement with fracture repair and soft tissue reconstruction is controversial. This study focuses on the efficacy of early single-stage repair in combined bony and soft tissue injuries. Retrospective review. Twenty-three patients with combined open soft tissue wounds and orbital fractures were studied for single-stage orbital reconstruction and periorbital soft tissue repair. Inclusion criteria were open soft tissue wounds with clinical and radiographic evidence of orbital fractures and repair performed within 48 h after injury. Surgical complications and reconstructive outcomes were assessed over 6 months. The main outcome measures were enophthalmos, pre- and post-CT imaging of orbits, scar evaluation, presence of diplopia, and eyelid position. Enophthalmos was corrected in 16/19 cases and improved in 3/19 cases. 3D reconstruction of CT images showed markedly improved orbital alignment with objective measurements of the optic foramen to cornea distance (mm) in reconstructed orbits relative to intact orbits of 0.66, 95% confidence interval [CI] (lower 0.33, upper 0.99) mm. The mean baseline of Stony Brook Scar Evaluation Scale was 0.6, 95%CI (0.30-0.92), and for 6 months, the mean score was 3.4, 95%CI (3.05-3.73). Residual diplopia in secondary gazes was present in two patients; one patient had ectropion. Complications included one case of local wound infection. An early single-stage repair of combined soft tissue and orbital fractures yields satisfactory functional and aesthetic outcomes. Complications are low and likely related to trauma severity. Copyright © 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Comment: Respecifying Emotional Influence

PubMed Central

Parkinson, Brian

2017-01-01

To what extent does the level of overlap between social appraisal and social referencing depend upon the particular definitions adopted when following different research agendas? I argue that processes of both kinds fall under the more inclusive heading of relation alignment. Relation alignment also covers emotional influence that is not mediated by the communication of appraisal. Similarities, interdependences, and distinctions between these various relation-alignment processes warrant further investigation. PMID:28804511
Comment: Respecifying Emotional Influence.

PubMed

Parkinson, Brian

2017-07-01

To what extent does the level of overlap between social appraisal and social referencing depend upon the particular definitions adopted when following different research agendas? I argue that processes of both kinds fall under the more inclusive heading of relation alignment. Relation alignment also covers emotional influence that is not mediated by the communication of appraisal. Similarities, interdependences, and distinctions between these various relation-alignment processes warrant further investigation.
Initial Navigation Alignment of Optical Instruments on GOES-R

NASA Astrophysics Data System (ADS)

Isaacson, P.; DeLuccia, F.; Reth, A. D.; Igli, D. A.; Carter, D.

2016-12-01

The GOES-R satellite is the first in NOAA's next-generation series of geostationary weather satellites. In addition to a number of space weather sensors, it will carry two principal optical earth-observing instruments, the Advanced Baseline Imager (ABI) and the Geostationary Lightning Mapper (GLM). During launch, currently scheduled for November of 2016, the alignment of these optical instruments is anticipated to shift from that measured during pre-launch characterization. While both instruments have image navigation and registration (INR) processing algorithms to enable automated geolocation of the collected data, the launch-derived misalignment may be too large for these approaches to function without an initial adjustment to calibration parameters. The parameters that may require adjustment are for Line of Sight Motion Compensation (LMC), and the adjustments will be estimated on orbit during the post-launch test (PLT) phase. We have developed approaches to estimate the initial alignment errors for both ABI and GLM image products. Our approaches involve comparison of ABI and GLM images collected during PLT to a set of reference ("truth") images using custom image processing tools and other software (the INR Performance Assessment Tool Set, or "IPATS") being developed for other INR assessments of ABI and GLM data. IPATS is based on image correlation approaches to determine offsets between input and reference images, and these offsets are the fundamental input to our estimate of the initial alignment errors. Initial testing of our alignment algorithms on proxy datasets lends high confidence that their application will determine the initial alignment errors to within sufficient accuracy to enable the operational INR processing approaches to proceed in a nominal fashion. We will report on the algorithms, implementation approach, and status of these initial alignment tools being developed for the GOES-R ABI and GLM instruments.
Formation of Highly Aligned Collagen Nanofibers by Continuous Cyclic Stretch of a Collagen Hydrogel Sheet.

PubMed

Nam, Eunryel; Lee, Won Chul; Takeuchi, Shoji

2016-07-01

A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The rearrangement of the collagen fibers depends on the different process parameters of the cyclic stretch, including magnitude, frequency, and period of stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells cultivated on the highly aligned collagen sheet show alignment along the collagen fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling

PubMed Central

Levy, Miguel; Karki, Dolendra

2017-01-01

We present a formulation of electromagnetic spin-orbit coupling in magneto-optic media, and propose an alternative source of spin-orbit coupling to non-paraxial optics vortices. Our treatment puts forth a formulation of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media. It shows that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to unequal spin to orbital angular momentum conversion in magneto-optic media evanescent waves in opposite propagation-directions. Generation of free-space helicoidal beams based on this conversion is shown to be spin-helicity- and magnetization-dependent. We show that transverse-spin to orbital angular momentum coupling into magneto-optic waveguide media engenders spin-helicity-dependent unidirectional propagation. This unidirectional effect produces different orbital angular momenta in opposite directions upon excitation-spin-helicity reversals. PMID:28059120
Characterization of the HD 17156 planetary system

NASA Astrophysics Data System (ADS)

Barbieri, M.; Alonso, R.; Desidera, S.; Sozzetti, A.; Martinez Fiorenzano, A. F.; Almenara, J. M.; Cecconi, M.; Claudi, R. U.; Charbonneau, D.; Endl, M.; Granata, V.; Gratton, R.; Laughlin, G.; Loeillet, B.; EXOPLANET Amateur Consortium

2009-08-01

Aims: We present data to improve the known parameters of the HD 17156 system (peculiar due to the eccentricity and long orbital period of its transiting planet) and constrain the presence of stellar companions. Methods: Photometric data were acquired for 4 transits, and high precision radial velocity measurements were simultaneously acquired with the SARG spectrograph at TNG for one transit. The template spectra of HD 17156 was used to derive effective temperature, gravity, and metallicity. A fit of the photometric and spectroscopic data was performed to measure the stellar and planetary radii, and the spin-orbit alignment. Planet orbital elements and ephemeris were derived from the fit. Near infrared adaptive optic images were acquired with the AdOpt module of TNG. Results: We found that the star has a radius of RS = 1.44±0.03 R_⊙ and the planet RP = 1.02±0.08 RJ. The transit ephemeris is Tc = 2 454 756.73134 ± 0.00020 + N \\cdot 21.21663 ± 0.00045 BJD. Analysis of the Rossiter-Mclaughlin effect shows that the system is spin orbit aligned with an angle β = 4.8°±5.3°. The analysis of high resolution images did not reveal any stellar companion with a projected separation between of 150 and 1 000 AU from HD 17156. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Based on observations collected at Asiago observatory, at Observatoire de Haute Provence and with Telast at IAC. Photometry and radial velocity data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/503/601
Quantitative regulation of bone-mimetic, oriented collagen/apatite matrix structure depends on the degree of osteoblast alignment on oriented collagen substrates.

PubMed

Matsugaki, Aira; Isobe, Yoshihiro; Saku, Taro; Nakano, Takayoshi

2015-02-01

Bone tissue has a specific anisotropic morphology derived from collagen fiber alignment and the related apatite crystal orientation as a bone quality index. However, the precise mechanism of cellular regulation of the crystallographic orientation of apatite has not been clarified. In this study, anisotropic construction of cell-produced mineralized matrix in vitro was established by initiating organized cellular alignment and subsequent oriented bone-like matrix (collagen/apatite) production. The oriented collagen substrates with three anisotropic levels were prepared by a hydrodynamic method. Primary osteoblasts were cultured on the fabricated substrates until mineralized matrix formation is confirmed. Osteoblast alignment was successfully regulated by the level of substrate collagen orientation, with preferential alignment along the direction of the collagen fibers. Notably, both fibrous orientation of newly synthesized collagen matrix and c-axis of produced apatite crystals showed preferential orientation along the cell direction. Because the degree of anisotropy of the deposited apatite crystals showed dependency on the directional distribution of osteoblasts cultured on the oriented collagen substrates, the cell orientation determines the crystallographic anisotropy of produced apatite crystals. To the best of our knowledge, this is the first report demonstrating that bone tissue anisotropy, even the alignment of apatite crystals, is controllable by varying the degree of osteoblast alignment via regulating the level of substrate orientation. © 2014 Wiley Periodicals, Inc.
Simplification of the time-dependent generalized self-interaction correction method using two sets of orbitals: Application of the optimized effective potential formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messud, J.; Dinh, P. M.; Suraud, Eric

2009-10-15

We propose a simplification of the time-dependent self-interaction correction (TD-SIC) method using two sets of orbitals, applying the optimized effective potential (OEP) method. The resulting scheme is called time-dependent 'generalized SIC-OEP'. A straightforward approximation, using the spatial localization of one set of orbitals, leads to the 'generalized SIC-Slater' formalism. We show that it represents a great improvement compared to the traditional SIC-Slater and Krieger-Li-Iafrate formalisms.
Simplification of the time-dependent generalized self-interaction correction method using two sets of orbitals: Application of the optimized effective potential formalism

NASA Astrophysics Data System (ADS)

Messud, J.; Dinh, P. M.; Reinhard, P.-G.; Suraud, Eric

2009-10-01

We propose a simplification of the time-dependent self-interaction correction (TD-SIC) method using two sets of orbitals, applying the optimized effective potential (OEP) method. The resulting scheme is called time-dependent “generalized SIC-OEP.” A straightforward approximation, using the spatial localization of one set of orbitals, leads to the “generalized SIC-Slater” formalism. We show that it represents a great improvement compared to the traditional SIC-Slater and Krieger-Li-Iafrate formalisms.
A radial measurement of the galaxy tidal alignment magnitude with BOSS data

NASA Astrophysics Data System (ADS)

Martens, Daniel; Hirata, Christopher M.; Ross, Ashley J.; Fang, Xiao

2018-07-01

The anisotropy of galaxy clustering in redshift space has long been used to probe the rate of growth of cosmological perturbations. However, if galaxies are aligned by large-scale tidal fields, then a sample with an orientation-dependent selection effect has an additional anisotropy imprinted on to its correlation function. We use the LOWZ and CMASS catalogues of SDSS-III BOSS Data Release 12 to divide galaxies into two subsamples based on their offset from the Fundamental Plane, which should be correlated with orientation. These subsamples must trace the same underlying cosmology, but have opposite orientation-dependent selection effects. We measure the clustering parameters of each subsample and compare them in order to calculate the dimensionless parameter B, a measure of how strongly galaxies are aligned by gravitational tidal fields. We found that for CMASS (LOWZ), the measured B was -0.024 ± 0.015 (-0.030 ± 0.016). This result can be compared to the theoretical predictions of Hirata, who argued that since galaxy formation physics does not depend on the direction of the `observer,' the same intrinsic alignment parameters that describe galaxy-ellipticity correlations should also describe intrinsic alignments in the radial direction. We find that the ratio of observed to theoretical values is 0.51 ± 0.32 (0.77 ± 0.41) for CMASS (LOWZ). We combine the results to obtain a total Obs/Theory = 0.61 ± 0.26. This measurement constitutes evidence (between 2σand 3σ) for radial intrinsic alignments, and is consistent with theoretical expectations (<2σ difference).
A Radial Measurement of the Galaxy Tidal Alignment Magnitude with BOSS Data

NASA Astrophysics Data System (ADS)

Martens, Daniel; Hirata, Christopher M.; Ross, Ashley J.; Fang, Xiao

2018-05-01

The anisotropy of galaxy clustering in redshift space has long been used to probe the rate of growth of cosmological perturbations. However, if galaxies are aligned by large-scale tidal fields, then a sample with an orientation-dependent selection effect has an additional anisotropy imprinted onto its correlation function. We use the LOWZ and CMASS catalogs of SDSS-III BOSS Data Release 12 to divide galaxies into two sub-samples based on their offset from the Fundamental Plane, which should be correlated with orientation. These sub-samples must trace the same underlying cosmology, but have opposite orientation-dependent selection effects. We measure the clustering parameters of each sub-sample and compare them in order to calculate the dimensionless parameter B, a measure of how strongly galaxies are aligned by gravitational tidal fields. We found that for CMASS (LOWZ), the measured B was -0.024 ± 0.015 (-0.030 ± 0.016). This result can be compared to the theoretical predictions of Hirata (2009), who argued that since galaxy formation physics does not depend on the direction of the "observer," the same intrinsic alignment parameters that describe galaxy-ellipticity correlations should also describe intrinsic alignments in the radial direction. We find that the ratio of observed to theoretical values is 0.51 ± 0.32 (0.77 ± 0.41) for CMASS (LOWZ). We combine the results to obtain a total Obs/Theory = 0.61 ± 0.26. This measurement constitutes evidence (between 2 and 3σ) for radial intrinsic alignments, and is consistent with theoretical expectations (<2σ difference).
The hierarchical nature of the spin alignment of dark matter haloes in filaments

NASA Astrophysics Data System (ADS)

Aragon-Calvo, M. A.; Yang, Lin Forrest

2014-05-01

Dark matter haloes in cosmological filaments and walls have (in average) their spin vector aligned with their host structure. While haloes in walls are aligned with the plane of the wall independently of their mass, haloes in filaments present a mass-dependent two-regime orientation. Here, we show that the transition mass determining the change in the alignment regime (from parallel to perpendicular) depends on the hierarchical level in which the halo is located, reflecting the hierarchical nature of the Cosmic Web. By explicitly exposing the hierarchical structure of the Cosmic Web, we are able to identify the contributions of different components of the filament network to the alignment signal. We propose a unifying picture of angular momentum acquisition that is based on the results presented here and previous results found by other authors. In order to do a hierarchical characterization of the Cosmic Web, we introduce a new implementation of the multiscale morphology filter, the MMF-2, that significantly improves the identification of structures and explicitly describes their hierarchy. L36
How the cosmic web induces intrinsic alignments of galaxies

NASA Astrophysics Data System (ADS)

Codis, S.; Dubois, Y.; Pichon, C.; Devriendt, J.; Slyz, A.

2016-10-01

Intrinsic alignments are believed to be a major source of systematics for future generation of weak gravitational lensing surveys like Euclid or LSST. Direct measurements of the alignment of the projected light distribution of galaxies in wide field imaging data seem to agree on a contamination at a level of a few per cent of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use dark matter-only simulations as the sole resource to predict and control intrinsic alignments. We report here estimates on the level of intrinsic alignment in the cosmological hydrodynamical simulation Horizon-AGN that could be a major source of systematic errors in weak gravitational lensing measurements. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, we show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. We will also present theoretical calculations that illustrate and qualitatively explain the observed signals.
A single-electron picture based on the multiconfiguration time-dependent Hartree-Fock method: application to the anisotropic ionization and subsequent high-harmonic generation of the CO molecule

NASA Astrophysics Data System (ADS)

Ohmura, S.; Kato, T.; Oyamada, T.; Koseki, S.; Ohmura, H.; Kono, H.

2018-02-01

The mechanisms of anisotropic near-IR tunnel ionization and high-order harmonic generation (HHG) in a CO molecule are theoretically investigated by using the multiconfiguration time-dependent Hartree-Fock (MCTDHF) method developed for the simulation of multielectron dynamics of molecules. The multielectron dynamics obtained by numerically solving the equations of motion (EOMs) in the MCTDHF method is converted to a single orbital picture in the natural orbital representation where the first-order reduced density matrix is diagonalized. The ionization through each natural orbital is examined and the process of HHG is classified into different optical paths designated by a combinations of initial, intermediate and final natural orbitals. The EOMs for natural spin-orbitals are also derived within the framework of the MCTDHF, which maintains the first-order reduced density matrix to be a diagonal one throughout the time propagation of a many-electron wave function. The orbital dependent, time-dependent effective potentials that govern the dynamics of respective time-dependent natural orbitals are deduced from the derived EOMs, of which the temporal variation can be used to interpret the motion of the electron density associated with each natural spin-orbital. The roles of the orbital shape, multiorbital ionization, linear Stark effect and multielectron interaction in the ionization and HHG of a CO molecule are revealed by the effective potentials obtained. When the laser electric field points to the nucleus O from C, tunnel ionization from the C atom side is enhanced; a hump structure originating from multielectron interaction is then formed on the top of the field-induced distorted barrier of the HOMO effective potential. This hump formation, responsible for the directional anisotropy of tunnel ionization, restrains the influence of the linear Stark effect on the energy shifts of bound states.
Orbital structure in oscillating galactic potentials

NASA Astrophysics Data System (ADS)

Terzić, Balša; Kandrup, Henry E.

2004-01-01

Subjecting a galactic potential to (possibly damped) nearly periodic, time-dependent variations can lead to large numbers of chaotic orbits experiencing systematic changes in energy, and the resulting chaotic phase mixing could play an important role in explaining such phenomena as violent relaxation. This paper focuses on the simplest case of spherically symmetric potentials subjected to strictly periodic driving with the aim of understanding precisely why orbits become chaotic and under what circumstances they will exhibit systematic changes in energy. Four unperturbed potentials V0(r) were considered, each subjected to a time dependence of the form V(r, t) =V0(r)(1 +m0 sinωt). In each case, the orbits divide clearly into regular and chaotic, distinctions which appear absolute. In particular, transitions from regularity to chaos are seemingly impossible. Over finite time intervals, chaotic orbits subdivide into what can be termed `sticky' chaotic orbits, which exhibit no large-scale secular changes in energy and remain trapped in the phase-space region where they started; and `wildly' chaotic orbits, which do exhibit systematic drifts in energy as the orbits diffuse to different phase-space regions. This latter distinction is not absolute, transitions corresponding apparently to orbits penetrating a `leaky' phase-space barrier. The three different orbit types can be identified simply in terms of the frequencies for which their Fourier spectra have the most power. An examination of the statistical properties of orbit ensembles as a function of driving frequency ω allows us to identify the specific resonances that determine orbital structure. Attention focuses also on how, for fixed amplitude m0, such quantities as the mean energy shift, the relative measure of chaotic orbits and the mean value of the largest Lyapunov exponent vary with driving frequency ω and how, for fixed ω, the same quantities depend on m0.
Hot Jupiters Aren't As Lonely As We Thought

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-01-01

The Friends of Hot Jupiters (FOHJ) project is a systematic search for planetary- and stellar-mass companions in systems that have known hot Jupiters short-period, gas-giant planets. This survey has discovered that many more hot Jupiters may have companions than originally believed.Missing FriendsFOHJ was begun with the goal of better understanding the systems that host hot Jupiters, in order to settle several longstanding issues.The first problem was one of observational statistics. We know that roughly half of the Sun-like stars nearby are in binary systems, yet weve only discovered a handful of hot Jupiters around binaries. Are binary systems less likely to host hot Jupiters? Or have we just missed the binary companions in the hot-Jupiter-hosting systems weve seen so far?An additional issue relates to formation mechanisms. Hot Jupiters probably migrated inward from where they formed out beyond the ice lines in protoplanetary disks but how?This median-stacked image, obtained with adaptive optics, shows one of the newly-discovered stellar companions to a star hosting a hot Jupiter. The projected separation is ~180 AU. [Ngo et al. 2015]Observations reveal two populations of hot Jupiters: those with circular orbits aligned with their hosts spins, and those with eccentric, misaligned orbits. The former population support a migration model dominated by local planet-disk interactions, whereas the latter population suggest the hot Jupiters migrated through dynamical interactions with distant companions. A careful determination of the companion rate in hot-Jupiter-hosting systems could help establish the ability of these two models to explain the observed populations.Search for CompanionsThe FOHJ project began in 2012 and studied 51 systems hosting known, transiting hot Jupiters with roughly half on circular, aligned orbits and half on eccentric, misaligned orbits. The survey consisted of three different, complementary components:Study 1Lead author: Heather Knutson (Caltech)Technique: Long-term radial velocity monitoringSearching for: Planetary companions at 120 AU from the starStudy 2Lead author: Henry Ngo (Caltech)Technique: Adaptive-optics imagingSearching for: Stellar companions at 502000 AU from the starStudy 3Lead author: Danielle Piskorz (Caltech)Technique: SpectroscopySearching for: Any additional stellar companions at 125 AU from the starThe companion fraction found within Study 2, the adaptive-optics imagine search. The three curves show the total, the systems with hot Jupiters on aligned and circular orbits, and those with hot Jupiters on misaligned and eccentric orbits. [Ngo et al. 2015]Migration ImplicationsUsing these three different techniques, the team found a significant number of both planetary and stellar companions that had not been previously detected. After correcting their results for completeness, they found a multiple-star rate of ~50% for these systems, resolving the problem of the missing companions. So really, we just werent looking hard enough for the companions previously.Intriguingly, the binary companion rate found for these hot Jupiter systems is higher than the average rate for the field stars (which is below 25% for the semimajor-axis range the FOHJ studies are sensitive to). This suggests that companion stars may indeed play a role in hot Jupiter formation and migration.That said, none of the three studies found a significant difference in the binary fraction for aligned versus misaligned hot Jupiters which means that the answer is not as simple as thought, with companion stars causing the misaligned planets. Thus, while hot Jupiters friends may play a role in their formation and migration, we still have work to do in understanding what that role is.CitationDanielle Piskorz et al 2015 ApJ 814 148. doi:10.1088/0004-637X/814/2/148Henry Ngo et al 2015 ApJ 800 138. doi:10.1088/0004-637X/800/2/138Heather A. Knutson et al 2014 ApJ 785 126. doi:10.1088/0004-637X/785/2/126
Optimal matrix rigidity for stress fiber polarization in stem cells

PubMed Central

Rehfeldt, F.; Brown, A. E. X.; Discher, D. E.; Safran, S. A.

2010-01-01

The shape and differentiation of human mesenchymal stem cells is especially sensitive to the rigidity of their environment; the physical mechanisms involved are unknown. A theoretical model and experiments demonstrate here that the polarization/alignment of stress-fibers within stem cells is a non-monotonic function of matrix rigidity. We treat the cell as an active elastic inclusion in a surrounding matrix whose polarizability, unlike dead matter, depends on the feedback of cellular forces that develop in response to matrix stresses. The theory correctly predicts the monotonic increase of the cellular forces with the matrix rigidity and the alignment of stress-fibers parallel to the long axis of cells. We show that the anisotropy of this alignment depends non-monotonically on matrix rigidity and demonstrate it experimentally by quantifying the orientational distribution of stress-fibers in stem cells. These findings offer a first physical insight for the dependence of stem cell differentiation on tissue elasticity. PMID:20563235
Simulation-based comprehensive benchmarking of RNA-seq aligners

PubMed Central

Baruzzo, Giacomo; Hayer, Katharina E; Kim, Eun Ji; Di Camillo, Barbara; FitzGerald, Garret A; Grant, Gregory R

2018-01-01

Alignment is the first step in most RNA-seq analysis pipelines, and the accuracy of downstream analyses depends heavily on it. Unlike most steps in the pipeline, alignment is particularly amenable to benchmarking with simulated data. We performed a comprehensive benchmarking of 14 common splice-aware aligners for base, read, and exon junction-level accuracy and compared default with optimized parameters. We found that performance varied by genome complexity, and accuracy and popularity were poorly correlated. The most widely cited tool underperforms for most metrics, particularly when using default settings. PMID:27941783
Hyperfine-Structure-Induced Depolarization of Impulsively Aligned I2 Molecules

NASA Astrophysics Data System (ADS)

Thomas, Esben F.; Søndergaard, Anders A.; Shepperson, Benjamin; Henriksen, Niels E.; Stapelfeldt, Henrik

2018-04-01

A moderately intense 450 fs laser pulse is used to create rotational wave packets in gas phase I2 molecules. The ensuing time-dependent alignment, measured by Coulomb explosion imaging with a delayed probe pulse, exhibits the characteristic revival structures expected for rotational wave packets but also a complex nonperiodic substructure and decreasing mean alignment not observed before. A quantum mechanical model attributes the phenomena to coupling between the rotational angular momenta and the nuclear spins through the electric quadrupole interaction. The calculated alignment trace agrees very well with the experimental results.
Non-metal spintronics: study of spin-dependent transport in InSb- and InAs-based nanopatterned heterostructures

NASA Astrophysics Data System (ADS)

Heremans, J. J.; Chen, Hong; Peters, J. A.; Goel, N.; Chung, S. J.; Santos, M. B.; van Roy, W.; Borghs, G.

2006-03-01

Spin-orbit interaction in semiconductor heterostructures can lead to various spin-dependent electronic transport effects without the presence of magnetic materials. Mesoscopic samples were fabricated on InSb/InAlSb and InAs/AlGaSb two-dimensional electron systems, where spin-orbit interaction is strong. In mesoscopic devices, the effects of spin-orbit interaction are not averaged out over the geometry, and lead to observable electronic properties. We experimentally demonstrate spin-split ballistic transport and the creation of fully spin-polarized electron beams using spin-dependent reflection geometries and transverse magnetic focusing geometries. Spin-dependent transport properties in the semiconductor materials are also investigated using antidot lattices. Spin-orbit interaction effects in high-mobility semiconductor devices may be utilized toward the design of novel spintronics implementations. We acknowledge NSF DMR-0094055 (JJH), DMR-0080054, DMR-0209371 (MBS).

Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow.

PubMed

Ghim, Mean; Alpresa, Paola; Yang, Sung-Wook; Braakman, Sietse T; Gray, Stephen G; Sherwin, Spencer J; van Reeuwijk, Maarten; Weinberg, Peter D

2017-11-01

Transport of macromolecules across vascular endothelium and its modification by fluid mechanical forces are important for normal tissue function and in the development of atherosclerosis. However, the routes by which macromolecules cross endothelium, the hemodynamic stresses that maintain endothelial physiology or trigger disease, and the dependence of transendothelial transport on hemodynamic stresses are controversial. We visualized pathways for macromolecule transport and determined the effect on these pathways of different types of flow. Endothelial monolayers were cultured under static conditions or on an orbital shaker producing different flow profiles in different parts of the wells. Fluorescent tracers that bound to the substrate after crossing the endothelium were used to identify transport pathways. Maps of tracer distribution were compared with numerical simulations of flow to determine effects of different shear stress metrics on permeability. Albumin-sized tracers dominantly crossed the cultured endothelium via junctions between neighboring cells, high-density lipoprotein-sized tracers crossed at tricellular junctions, and low-density lipoprotein-sized tracers crossed through cells. Cells aligned close to the angle that minimized shear stresses across their long axis. The rate of paracellular transport under flow correlated with the magnitude of these minimized transverse stresses, whereas transport across cells was uniformly reduced by all types of flow. These results contradict the long-standing two-pore theory of solute transport across microvessel walls and the consensus view that endothelial cells align with the mean shear vector. They suggest that endothelial cells minimize transverse shear, supporting its postulated proatherogenic role. Preliminary data show that similar tracer techniques are practicable in vivo. NEW & NOTEWORTHY Solutes of increasing size crossed cultured endothelium through intercellular junctions, through tricellular junctions, or transcellularly. Cells aligned to minimize the shear stress acting across their long axis. Paracellular transport correlated with the level of this minimized shear, but transcellular transport was reduced uniformly by flow regardless of the shear profile. Copyright © 2017 the American Physiological Society.
Sunlit Io Atmospheric [O I] 6300 A and the Plasma Torus

NASA Technical Reports Server (NTRS)

Oliversen, Ronald J.; Scherb, Frank; Smyth, William H.; Freed, Melanie E.; Woodward, R. Carey, Jr.; Marcone, Maximus L.; Retherford, Kurt D.; Lupie, Olivia L.; Morgenthaler, Jeffrey P.; Fisher, Richard R. (Technical Monitor)

2001-01-01

A large database of sunlit Io [O I] 6300A emission, acquired over the period 1990-1999, with extensive coverage of Io orbital phase angle phi and System III longitude lambda(sub III), exhibits significant long-term and short-term variations in [O I] 6300A emission intensities. The long-term average intensity shows a clear dependence on lambda(sub III), which establishes conclusively that the emission is produced by the interaction between Io's atmosphere and the plasma torus. Two prominent average intensity maxima, 70 deg to 90 deg wide, are centered at lambda(sub III) about 130deg. and about 295 deg. A comparison of data from October 1998 with a three-dimensional plasma torus model, based upon electron impact excitation of atomic oxygen, suggests a basis for study of the torus interaction with Io's atmosphere. The observed short-term, erratic [O I] 6300A intensity variations fluctuate approximately 20% to 50% on time scale of tens of minutes with less frequent fluctuations of a factor of about 2. The most likely candidate to produce these fluctuations is a time-variable energy flux of field-aligned nonthermal electrons identified recently in Galileo PLS data. If true, the short-term [O I] intensity fluctuations may be related to variable field-aligned currents driven by inward and outward torus plasma transport and/or transient high-latitude, field-aligned potential drops. A correlation between the intensity and emission line width indicates molecular dissociation may contribute significantly to the [O I] 6300A emission. The nonthermal electron energy flux may produce O(1-D) by electron impact dissociation of SO2 and SO, with the excess energy going into excitation of O and its kinetic energy. The [O I] 6300A emission database establishes Io as a valuable probe of the torus, responding to local conditions at Io's position.
Constraining the Properties of the Eta Carinae System via 3-D SPH Models of Space-Based Observations: The Absolute Orientation of the Binary Orbit

NASA Technical Reports Server (NTRS)

Madura, Thomas I.; Gull, Theodore R.; Owocki, Stanley P.; Okazaki, Atsuo T.; Russell, Christopher M. P.

2010-01-01

The extremely massive (> 90 Solar Mass) and luminous (= 5 x 10(exp 6) Solar Luminosity) star Eta Carinae, with its spectacular bipolar "Homunculus" nebula, comprises one of the most remarkable and intensely observed stellar systems in the galaxy. However, many of its underlying physical parameters remain a mystery. Multiwavelength variations observed to occur every 5.54 years are interpreted as being due to the collision of a massive wind from the primary star with the fast, less dense wind of a hot companion star in a highly elliptical (e approx. 0.9) orbit. Using three-dimensional (3-D) Smoothed Particle Hydrodynamics (SPH) simulations of the binary wind-wind collision in Eta Car, together with radiative transfer codes, we compute synthetic spectral images of [Fe III] emission line structures and compare them to existing Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations. We are thus able, for the first time, to constrain the absolute orientation of the binary orbit on the sky. An orbit with an inclination of i approx. 40deg, an argument of periapsis omega approx. 255deg, and a projected orbital axis with a position angle of approx. 312deg east of north provides the best fit to the observations, implying that the orbital axis is closely aligned in 3-1) space with the Homunculus symmetry axis, and that the companion star orbits clockwise on the sky relative to the primary.
Constraining the Properties of the Eta Carinae System via 3-D SPH Models of Space-Based Observations: The Absolute Orientation of the Binary Orbit

NASA Technical Reports Server (NTRS)

Madura, Thomas I.; Gull, Theodore R.; Owocki, Stanley P.; Okazaki, Atsuo T.; Russell, Christopher M. P.

2011-01-01

The extremely massive (> 90 Stellar Mass) and luminous (= 5 x 10(exp 6) Stellar Luminosity) star Eta Carinae, with its spectacular bipolar "Homunculus" nebula, comprises one of the most remarkable and intensely observed stellar systems in the Galaxy. However, many of its underlying physical parameters remain unknown. Multiwavelength variations observed to occur every 5.54 years are interpreted as being due to the collision of a massive wind from the primary star with the fast, less dense wind of a hot companion star in a highly elliptical (e approx. 0.9) orbit. Using three-dimensional (3-D) Smoothed Particle Hydrodynamics (SPH) simulations of the binary wind-wind collision, together with radiative transfer codes, we compute synthetic spectral images of [Fe III] emission line structures and compare them to existing Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations. We are thus able, for the first time, to tightly constrain the absolute orientation of the binary orbit on the sky. An orbit with an inclination of approx. 40deg, an argument of periapsis omega approx. 255deg, and a projected orbital axis with a position angle of approx. 312deg east of north provides the best fit to the observations, implying that the orbital axis is closely aligned in 3-D space with the Homunculus symmetry axis, and that the companion star orbits clockwise on the sky relative to the primary.
Synthesis, Spectra, and Theoretical Investigations of 1,3,5-Triazines Compounds as Ultraviolet Rays Absorber Based on Time-Dependent Density Functional Calculations and three-Dimensional Quantitative Structure-Property Relationship.

PubMed

Wang, Xueding; Xu, Yilian; Yang, Lu; Lu, Xiang; Zou, Hao; Yang, Weiqing; Zhang, Yuanyuan; Li, Zicheng; Ma, Menglin

2018-03-01

A series of 1,3,5-triazines were synthesized and their UV absorption properties were tested. The computational chemistry methods were used to construct quantitative structure-property relationship (QSPR), which was used to computer aided design of new 1,3,5-triazines ultraviolet rays absorber compounds. The experimental UV absorption data are in good agreement with those predicted data using the Time-dependent density functional theory (TD-DFT) [B3LYP/6-311 + G(d,p)]. A suitable forecasting model (R > 0.8, P < 0.0001) was revealed. Predictive three-dimensional quantitative structure-property relationship (3D-QSPR) model was established using multifit molecular alignment rule of Sybyl program, which conclusion is consistent with the TD-DFT calculation. The exceptional photostability mechanism of such ultraviolet rays absorber compounds was studied and confirmed as principally banked upon their ability to undergo excited-state deactivation via an ultrafast excited-state proton transfer (ESIPT). The intramolecular hydrogen bond (IMHB) of 1,3,5-triazines compounds is the basis for the excited state proton transfer, which was explored by IR spectroscopy, UV spectra, structural and energetic aspects of different conformers and frontier molecular orbitals analysis.
Active Debris Removal Using Modified Launch Vehicle Upper Stages

NASA Astrophysics Data System (ADS)

Nasseri, S. Ali; Emanuelli, Matteo; Raval, Siddharth; Turconi, Andrea

2013-09-01

During the past few years, several research programs have assessed the current state and future evolution of space debris in the Low Earth Orbit region. These studies indicate that space debris density could reach a critical level such that there will be a continuous increase in the number of debris objects, primarily driven by debris-debris collision activity known as the Kessler effect. These studies also highlight the urgency for active debris removal.An Active Debris Removal System (ADRS) is capable of approaching the debris object through a close-range rendezvous, stabilizing its attitude, establishing physical contact, and finally de-orbiting the debris object. The de-orbiting phase could be powered by propulsion systems such as chemical rockets or electrodynamic tether (EDT) systems.The aim of this project is to model and evaluate a debris removal mission in which an adapted rocket upper stage, equipped with an electrodynamic tether (EDT) system, is employed for de-orbiting a debris object. This ADRS package is installed initially as part of a launch vehicle on a normal satellite deployment mission, and a far-approach manoeuvre will be required to align the ADRS' orbit with that of the target debris. We begin by selecting a suitable target debris and launch vehicle, and then proceed with modelling the entire debris removal mission from launch to de-orbiting of the target debris object using Analytical Graphic Inc.'s Systems Tool Kit (STK).
The effect of surface alignment on analog control of director rotation in polarization stiffened SmC* devices

NASA Astrophysics Data System (ADS)

Reznikov, Mitya; Lopatina, Lena M.; O'Callaghan, Michael J.; Bos, Philip J.

2011-03-01

The effect of surface alignment on the achievement of analog ("V"-shaped) electric field control of director rotation in SmC* liquid crystal devices is investigated experimentally and through numerical modeling. Ferroelectric SmC* liquid crystals are intrinsically analog and thresholdless, i.e. the director can be rotated freely around the tilt cone. Whether or not a SmC* liquid crystal cell exhibits thresholdless switching depends strongly on the influence of the cell's alignment layers, on the magnitude of the liquid crystal's spontaneous polarization, and on whether smectic layers adopt a bookshelf or chevron configuration. To study the effect of the surface alignment layers, we have exploited a technique for the vertical (bookshelf) alignment of the smectic layers that does not depend on surface anisotropy. The alignment technique allows an experimental study of the influence of surfaces spanning a wide range of pretilt angles, azimuthal and zenithal anchoring energies. This technique is used to study the effect of surfaces on the threshold behavior of director rotation in SmC* materials under the influence of an electric field. The alignment technique also allowed us to use a high-PS liquid crystal material having an I-A-C phase sequence and reduced layer shrinkage thought to be well suited to thresholdless switching. We show that the alignment layer has a strong effect, and that excellent analog response can be achieved for the case of alignment layers which promote homeotropic director orientation. We further model and discuss the potential effect of a thin layer of nematic at the surface and the possibility of gliding of the easy axis during switching.
27 T ultra-high static magnetic field changes orientation and morphology of mitotic spindles in human cells

PubMed Central

Zhang, Lei; Hou, Yubin; Li, Zhiyuan; Ji, Xinmiao; Wang, Ze; Wang, Huizhen; Tian, Xiaofei; Yu, Fazhi; Yang, Zhenye; Pi, Li; Mitchison, Timothy J; Lu, Qingyou; Zhang, Xin

2017-01-01

Purified microtubules have been shown to align along the static magnetic field (SMF) in vitro because of their diamagnetic anisotropy. However, whether mitotic spindle in mammalian cells can be aligned by magnetic field has not been experimentally proved. In particular, the biological effects of SMF of above 20 T (Tesla) on mammalian cells have never been reported. Here we found that in both CNE-2Z and RPE1 human cells spindle orients in 27 T SMF. The direction of spindle alignment depended on the extent to which chromosomes were aligned to form a planar metaphase plate. Our results show that the magnetic torque acts on both microtubules and chromosomes, and the preferred direction of spindle alignment relative to the field depends more on chromosome alignment than microtubules. In addition, spindle morphology was also perturbed by 27 T SMF. This is the first reported study that investigated the mammalian cellular responses to ultra-high magnetic field of above 20 T. Our study not only found that ultra-high magnetic field can change the orientation and morphology of mitotic spindles, but also provided a tool to probe the role of spindle orientation and perturbation in developmental and cancer biology. DOI: http://dx.doi.org/10.7554/eLife.22911.001 PMID:28244368
Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures

NASA Astrophysics Data System (ADS)

Amalokwu, Kelvin; Chapman, Mark; Best, Angus I.; Minshull, Timothy A.; Li, Xiang-Yang

2015-08-01

The seismic properties of rocks are known to be sensitive to partial liquid or gas saturation, and to aligned fractures. P-wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid. However, studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface. An understanding of the effects of partial liquid or gas saturation on P-wave anisotropy could help improve seismic characterization of fractured, gas bearing reservoirs. Using octagonal-shaped synthetic sandstone samples, one containing aligned penny-shaped fractures and the other without fractures, we examined the influence of water saturation on P-wave anisotropy in fractured rocks. In the fractured rock, the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures. Consequently, the anisotropy parameter `ε' decreases as a result of this fluid stiffening effect. These effects are frequency dependent as a result of wave-induced fluid flow mechanisms. Our observations can be explained by combining a frequency-dependent fractured rock model and a frequency-dependent partial saturation model.
Orbit Selection for Earth Observation Missions

NASA Technical Reports Server (NTRS)

King, J. C.

1978-01-01

The orbit selection process is simplified for most earth-oriented satellite missions by a restriction to circular orbits, which reduces the primary orbit characteristics to be determined to only two: altitude and inclination. A number of important mission performance characteristics depend on these choices, however, so a major part of the orbit selection task is concerned with developing the correlating relationships in clear and convenient forms to provide a basis for rational orbit selection procedures. The present approach to that task is organized around two major areas of mission performance, orbit plane precession and coverage pattern development, whose dependence on altitude and inclination is delineated graphically in design chart form. These charts provide a visual grasp of the relationships between the quantities cited above, as well as other important mission performance parameters including viewing time of day (solar), sensor swath width (and fields of view), swath sequencing, and pattern repeat condition and repeat periods.
Communication: Time-dependent optimized coupled-cluster method for multielectron dynamics

NASA Astrophysics Data System (ADS)

Sato, Takeshi; Pathak, Himadri; Orimo, Yuki; Ishikawa, Kenichi L.

2018-02-01

Time-dependent coupled-cluster method with time-varying orbital functions, called time-dependent optimized coupled-cluster (TD-OCC) method, is formulated for multielectron dynamics in an intense laser field. We have successfully derived the equations of motion for CC amplitudes and orthonormal orbital functions based on the real action functional, and implemented the method including double excitations (TD-OCCD) and double and triple excitations (TD-OCCDT) within the optimized active orbitals. The present method is size extensive and gauge invariant, a polynomial cost-scaling alternative to the time-dependent multiconfiguration self-consistent-field method. The first application of the TD-OCC method of intense-laser driven correlated electron dynamics in Ar atom is reported.
Communication: Time-dependent optimized coupled-cluster method for multielectron dynamics.

PubMed

Sato, Takeshi; Pathak, Himadri; Orimo, Yuki; Ishikawa, Kenichi L

2018-02-07

Time-dependent coupled-cluster method with time-varying orbital functions, called time-dependent optimized coupled-cluster (TD-OCC) method, is formulated for multielectron dynamics in an intense laser field. We have successfully derived the equations of motion for CC amplitudes and orthonormal orbital functions based on the real action functional, and implemented the method including double excitations (TD-OCCD) and double and triple excitations (TD-OCCDT) within the optimized active orbitals. The present method is size extensive and gauge invariant, a polynomial cost-scaling alternative to the time-dependent multiconfiguration self-consistent-field method. The first application of the TD-OCC method of intense-laser driven correlated electron dynamics in Ar atom is reported.
Deriving stellar inclination of slow rotators using stellar activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dumusque, X., E-mail: xdumusque@cfa.harvard.edu

2014-12-01

Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than ∼2-2.5 km s{sup –1}. By using the new activity simulation SOAP 2.0 which can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit observations of solar-type stars and derive their inclination. For HD 189733, we estimate the stellar inclination to be i=84{sub −20}{sup +6} deg, which implies a star-planet obliquity of ψ=4{sub −4}{sup +18} considering previous measurements of the spin-orbit angle.more » For α Cen B, we derive an inclination of i=45{sub −19}{sup +9}, which implies that the rotational spin of the star is not aligned with the orbital spin of the α Cen binary system. In addition, assuming that α Cen Bb is aligned with its host star, no transit would occur. The inclination of α Cen B can be measured using 40 radial-velocity measurements, which is remarkable given that the projected rotational velocity of the star is smaller than 1.15 km s{sup –1}.« less
The Sentinel-4 UVN focal plane assemblies

NASA Astrophysics Data System (ADS)

Hinger, Jürgen; Hohn, Rüdiger; Gebhardt, Eyk; Reichardt, Jörg

2017-09-01

The Sentinel-4 UVN Instrument is a dispersive imaging spectrometer covering the UV-VIS and the NIR wavelength. It is developed and built under an ESA contract by an industrial consortium led by Airbus Defence and Space. It will be accommodated on board of the MTG-S (Meteosat Third Generation - Sounder) satellite that will be placed in a geostationary orbit over Europe sampling data for generating two-dimensional maps of a number of atmospheric trace gases. The incoming light is dispersed by reflective gratings and detected by the two (UVVIS and NIR) CCDs mounted inside the focal plane assemblies. Both CCD detectors acquire spectral channels and spatial sampling in two orthogonal directions and will be operated at about 215 K mainly to minimize random telegraph signal effects and to reduce dark current. Stringent detector temperature as well as alignment stability requirements of less than +/-0.1 K per day respectively of less than 2 micrometers/2 arcseconds from ground to orbit are driving the FPA thermo-mechanical design. A specific FPA design feature is the redundant LED-calibration system for bad pixel detection as well as pixel gain and linearity monitoring. This paper reports on the design and qualification of the Focal Plane Assemblies with emphasis on thermo-mechanical as well as alignment stability verification.
Impact of MoO3 interlayer on the energy level alignment of pentacene-C60 heterostructure.

PubMed

Zou, Ye; Mao, Hongying; Meng, Qing; Zhu, Daoben

2016-02-28

Using in situ ultraviolet photoelectron spectroscopy, the electronic structure evolutions at the interface between pentacene and fullerene (C60), a classical organic donor-acceptor heterostructure in organic electronic devices, on indium-tin oxide (ITO) and MoO3 modified ITO substrates have been investigated. The insertion of a thin layer MoO3 has a significant impact on the interfacial energy level alignment of pentacene-C60 heterostructure. For the deposition of C60 on pentacene, the energy difference between the highest occupied molecular orbital of donor and the lowest unoccupied molecular orbital of acceptor (HOMO(D)-LUMO(A)) offset of C60/pentacene heterostructure increased from 0.86 eV to 1.54 eV after the insertion of a thin layer MoO3 on ITO. In the inverted heterostructrure where pentacene was deposited on C60, the HOMO(D)-LUMO(A) offset of pentacene/C60 heterostructure increased from 1.32 to 2.20 eV after MoO3 modification on ITO. The significant difference of HOMO(D)-LUMO(A) offset shows the feasibility to optimize organic electronic device performance through interfacial engineering approaches, such as the insertion of a thin layer high work function MoO3 films.
The cosmic web and the orientation of angular momenta

NASA Astrophysics Data System (ADS)

Libeskind, Noam I.; Hoffman, Yehuda; Knebe, Alexander; Steinmetz, Matthias; Gottlöber, Stefan; Metuki, Ofer; Yepes, Gustavo

2012-03-01

We use a 64 h-1 Mpc dark-matter-only cosmological simulation to examine the large-scale orientation of haloes and substructures with respect to the cosmic web. A web classification scheme based on the velocity shear tensor is used to assign to each halo in the simulation a web type: knot, filament, sheet or void. Using ˜106 haloes that span ˜3 orders of magnitude in mass, the orientation of the halo's spin and the orbital angular momentum of subhaloes with respect to the eigenvectors of the shear tensor is examined. We find that the orbital angular momentum of subhaloes tends to align with the intermediate eigenvector of the velocity shear tensor for all haloes in knots, filaments and sheets. This result indicates that the kinematics of substructures located deep within the virialized regions of a halo is determined by its infall which in turn is determined by the large-scale velocity shear, a surprising result given the virialized nature of haloes. The non-random nature of subhalo accretion is thus imprinted on the angular momentum measured at z= 0. We also find that the haloes' spin axis is aligned with the third eigenvector of the velocity shear tensor in filaments and sheets: the halo spin axis points along filaments and lies in the plane of cosmic sheets.
DFT investigation on the electronic structure of Faujasite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popeneciu, Horea; Calborean, Adrian; Tudoran, Cristian

2013-11-13

We report here first-principle pseudopotential DFT calculations to investigate relevant aspects of the electronic structure of zeolites based FAU. Fundamental molecular issues of the band-gap and electronic population analysis were reviewed under GGA/RPBE level of theory, corroborated with a DZP basis set and Troullier-Martins norm conserving pseudo-potentials. The atom-projected density of states and the analysis of HOMO-LUMO frontier orbitals at Gamma point were performed. Their electronic transfers are discussed through the alignment and relative positions of orbitals in order to determine the way that the molecule interacts with adsorbed molecules and other practical applications. Mulliken population analysis was employed formore » describing atomic charge distribution in the chosen systems.« less
Off-axis points encoding/decoding with orbital angular momentum spectrum

PubMed Central

Chu, Jiaqi; Chu, Daping; Smithwitck, Quinn

2017-01-01

Encoding/decoding off-axis points with discrete orbital angular momentum (OAM) modes is investigated. On-axis Laguerre-Gaussian (LG) beams are expanded into off-axis OAM spectra, with which off-axis points are encoded. The influence of the mode and the displacement of the LG beam on the spread of the OAM spectrum is analysed. The results show that not only the conventional on-axis point, but also off-axis points, can be encoded and decoded with OAM of light. This is confirmed experimentally. The analytical result here provides a solid foundation to use OAM modes to encode two-dimensional high density information for multiplexing and to analyse the effect of mis-alignment in practical OAM applications. PMID:28272543
Orbital radar evidence for lunar subsurface layering in Maria Serenitatis and Crisium

NASA Technical Reports Server (NTRS)

Peeples, W. J.; Sill, W. R.; May, T. W.; Ward, S. H.; Phillips, R. J.; Jordan, R. L.; Abbott, E. A.; Killpack, T. J.

1978-01-01

Data from the lunar-orbiting Apollo 17 radar sounding experiment (60-m wavelength) have been examined in both digital and holographic formats, and it is concluded that there are two subsurface radar reflectors below the surface in Mare Serenitatis and one reflector below the surface in Mare Crisium. The mean apparent depths of the reflectors below the surface of the former Mare are 0.9 and 1.6 km, while the reflector below the surface of the latter Mare has a mean depth of 1.4 km. These reflectors represent basin-wide subsurface interfaces. Techniques for reducing surface backscatter (clutter) in the data are described, and reasons for thinking that the distinct alignments in radar returns represent subsurface reflecting horizons are explained
Molecular Gas Clumps from the Destruction of Icy Bodies in the beta Pictoris Debris Disk

NASA Technical Reports Server (NTRS)

Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; Augereau, J. -C.; Casassus, S.; Corder, S.; Greaves, J. S.; DeGregorio-Monsalvo, I.; Hales, A.; Jackson, A. P.;

2014-01-01

Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at sub-mm wavelengths of the archetypal debris disk around ß Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of the inner planet, beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

Generating millimeter-wave Bessel beam with orbital angular momentum using reflective-type metasurface inherently integrated with source

NASA Astrophysics Data System (ADS)

Shen, Yizhu; Yang, Jiawei; Meng, Hongfu; Dou, Wenbin; Hu, Sanming

2018-04-01

Metasurfaces, orbital angular momenta (OAM), and non-diffractive Bessel beams have been attracting worldwide research. Combining the benefits of these three promising techniques, this paper proposes a metasurface-based reflective-type approach to generate a first-order Bessel beam carrying OAM. To validate this approach, a millimeter-wave metasurface is analyzed, designed, fabricated, and measured. Experimental results agree well with simulation. Moreover, this reflective-type metasurface, generating a Bessel beam with OAM, is inherently integrated with a planar feeding source in the same single-layer printed circuit board. Therefore, the proposed design features low profile, low cost, easy integration with front-end active circuits, and no alignment error between the feeding source and the metasurface.
LDR segmented mirror technology assessment study

NASA Technical Reports Server (NTRS)

Krim, M.; Russo, J.

1983-01-01

In the mid-1990s, NASA plans to orbit a giant telescope, whose aperture may be as great as 30 meters, for infrared and sub-millimeter astronomy. Its primary mirror will be deployed or assembled in orbit from a mosaic of possibly hundreds of mirror segments. Each segment must be shaped to precise curvature tolerances so that diffraction-limited performance will be achieved at 30 micron (nominal operating wavelength). All panels must lie within 1 micron on a theoretical surface described by the optical precipitation of the telescope's primary mirror. To attain diffraction-limited performance, the issues of alignment and/or position sensing, position control of micron tolerances, and structural, thermal, and mechanical considerations for stowing, deploying, and erecting the reflector must be resolved. Radius of curvature precision influences panel size, shape, material, and type of construction. Two superior material choices emerged: fused quartz (sufficiently homogeneous with respect to thermal expansivity to permit a thin shell substrate to be drape molded between graphite dies to a precise enough off-axis asphere for optical finishing on the as-received a segment) and a Pyrex or Duran (less expensive than quartz and formable at lower temperatures). The optimal reflector panel size is between 1-1/2 and 2 meters. Making one, two-meter mirror every two weeks requires new approaches to manufacturing off-axis parabolic or aspheric segments (drape molding on precision dies and subsequent finishing on a nonrotationally symmetric dependent machine). Proof-of-concept developmental programs were identified to prove the feasibility of the materials and manufacturing ideas.
Radio-planetary from tie from Phobos-2 VLBI data

NASA Technical Reports Server (NTRS)

Hildebrand, C. E.; Iijima, B. A.; Kroger, P. M.; Folkner, W. M.; Edwards, C. D.

1994-01-01

In an ongoing effort to improve the knowledge of the relative orientation (the 'frame tie') of the planetary ephemeris reference frame used in deep navigation and a second reference frame that is defined by the coordinates of a set of extragalactic radio sources, VLBI observations of the Soviet Phobos-2 spacecraft and nearby (in angle) radio sources were obtained at two epochs in 1989, shortly after the spacecraft entered orbit about Mars. The frame tie is an important systematic error source affecting both interplanetary navigation and the process of improving the theory of the Earth's orientation. The data from a single Phobos-2 VLBI session measure one component of the direction vector from Earth to Mars in the frame of the extragalactic radio sources (the 'radio frame'). The radio frame has been shown to be stable and internally consistent with an accuracy of 5 nrad. The planetary ephemeris reference frame has an internal consistency of approximately 15 nrad. The planetary and radio source reference frames were aligned prior to 1989 and measurements of occulations of the radio source 3C273 by the Moon. The Phobos-2 VLBI measurements provide improvement in the accuracy of two of the three angles describing a general rotation between the planetary and radio reference frames. A complete set of measurements is not available because data acquisition was terminated prematurely by loss of spacecraft. The analysis of the two Phobos-2 VLBI data sets indicates that, in the directions of the two rotation components determined by these data, the JPL planetary ephemeris DE200 is aligned with the radio frame as adopted by the International Earth Rotation Service within an accuracy of 20-40 nrad, depending on direction. The limiting errors in the solutions for these offsets are spacecraft trajectory (20 nrad), instrumental biases (19 nrad), and dependence of quasar coordinates on observing frequency (24 nrad).
A refined orbit for the satellite of asteroid (107) Camilla

NASA Astrophysics Data System (ADS)

Pajuelo, Myriam Virginia; Carry, Benoit; Vachier, Frederic; Berthier, Jerome; Descamp, Pascal; Merline, William J.; Tamblyn, Peter M.; Conrad, Al; Storrs, Alex; Margot, Jean-Luc; Marchis, Frank; Kervella, Pierre; Girard, Julien H.

2015-11-01

The satellite of the Cybele asteroid (107) Camilla was discovered in March 2001 using the Hubble Space Telescope (Storrs et al., 2001, IAUC 7599). From a set of 23 positions derived from adaptive optics observations obtained over three years with the ESO VLT, Keck-II and Gemini-North telescopes, Marchis et al. (2008, Icarus 196) determined its orbit to be nearly circular.In the new work reported here, we compiled, reduced, and analyzed observations at 39 epochs (including the 23 positions previously analyzed) by adding additional observations taken from data archives: HST in 2001; Keck in 2002, 2003, and 2009; Gemini in 2010; and VLT in 2011. The present dataset hence contains twice as many epochs as the prior analysis and covers a time span that is three times longer (more than a decade).We use our orbit determination algorithm Genoid (GENetic Orbit IDentification), a genetic based algorithm that relies on a metaheuristic method and a dynamical model of the Solar System (Vachier et al., 2012, A&A 543). The method uses two models: a simple Keplerian model to minimize the search-time for an orbital solution, exploring a wide space of solutions; and a full N-body problem that includes the gravitational field of the primary asteroid up to 4th order.The orbit we derive fits all 39 observed positions of the satellite with an RMS residual of only milli-arcseconds, which corresponds to sub-pixel accuracy. We found the orbit of the satellite to be circular and roughly aligned with the equatorial plane of Camilla. The refined mass of the system is (12 ± 1) x 10^18 kg, for an orbital period of 3.71 days.We will present this improved orbital solution of the satellite of Camilla, as well as predictions for upcoming stellar occultation events.
Efficient construction of exchange and correlation potentials by inverting the Kohn-Sham equations.

PubMed

Kananenka, Alexei A; Kohut, Sviataslau V; Gaiduk, Alex P; Ryabinkin, Ilya G; Staroverov, Viktor N

2013-08-21

Given a set of canonical Kohn-Sham orbitals, orbital energies, and an external potential for a many-electron system, one can invert the Kohn-Sham equations in a single step to obtain the corresponding exchange-correlation potential, vXC(r). For orbitals and orbital energies that are solutions of the Kohn-Sham equations with a multiplicative vXC(r) this procedure recovers vXC(r) (in the basis set limit), but for eigenfunctions of a non-multiplicative one-electron operator it produces an orbital-averaged potential. In particular, substitution of Hartree-Fock orbitals and eigenvalues into the Kohn-Sham inversion formula is a fast way to compute the Slater potential. In the same way, we efficiently construct orbital-averaged exchange and correlation potentials for hybrid and kinetic-energy-density-dependent functionals. We also show how the Kohn-Sham inversion approach can be used to compute functional derivatives of explicit density functionals and to approximate functional derivatives of orbital-dependent functionals.
Theory of electronic and spin-orbit proximity effects in graphene on Cu(111)

NASA Astrophysics Data System (ADS)

Frank, Tobias; Gmitra, Martin; Fabian, Jaroslav

2016-04-01

We study orbital and spin-orbit proximity effects in graphene adsorbed to the Cu(111) surface by means of density functional theory (DFT). The proximity effects are caused mainly by the hybridization of graphene π and copper d orbitals. Our electronic structure calculations agree well with the experimentally observed features. We carry out a graphene-Cu(111) distance dependent study to obtain proximity orbital and spin-orbit coupling parameters, by fitting the DFT results to a robust low energy model Hamiltonian. We find a strong distance dependence of the Rashba and intrinsic proximity induced spin-orbit coupling parameters, which are in the meV and hundreds of μ eV range, respectively, for experimentally relevant distances. The Dirac spectrum of graphene also exhibits a proximity orbital gap, of about 20 meV. Furthermore, we find a band inversion within the graphene states accompanied by a reordering of spin and pseudospin states, when graphene is pressed towards copper.
KSC-98pc259

NASA Image and Video Library

1998-01-31

KENNEDY SPACE CENTER, FLA. -- STS-89 Commander Terrence Wilcutt, at left, shakes hands with Pilot Joe Edwards Jr. under the orbiter Endeavour after it landed on Runway 15 at KSC’s Shuttle Landing Facility Jan. 31. Kneeling in front of the wheel of the orbiter's nose, the commander and pilot congratulate each other on a perfect alignment of the wheel down the center of the runway. The 89th Space Shuttle mission was the 42nd (and 13th consecutive) landing of the orbiter at KSC, and STS-89 was the eighth of nine planned dockings of the orbiter with the Russian Space Station Mir. STS-89 Mission Specialist Andrew Thomas, Ph.D., succeeded NASA astronaut and Mir 24 crew member David Wolf, M.D., who was on the Russian space station since late September 1997. Dr. Wolf returned to Earth on Endeavour with the remainder of the STS-89 crew, including Commander Wilcutt; Pilot Edwards; and Mission Specialists James Reilly, Ph.D.; Michael Anderson; Bonnie Dunbar, Ph.D.; and Salizhan Sharipov of the Russian Space Agency. Dr. Thomas is scheduled to remain on Mir until the STS-91 Shuttle mission returns in June 1998. In addition to the docking and crew exchange, STS-89 included the transfer of science, logistical equipment and supplies between the two orbiting spacecrafts
Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

DOE PAGES

Kim, J. -W.; Choi, Y.; Chun, S. H.; ...

2018-03-26

Here, the combination of strong electron correlations in 3d transition metal oxides and spin-orbit interactions in the 5d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIrO 3 (SIO) and La 2/3Sr 1/3MnO 3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolvedmore » x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular-orbitals between the Mn and Ir layers modifying the Ir 5d electronic configuration through the mixture of t 2g and e g states, resulting in a deviation from J eff = ½. This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5d states with 2-dimensional 3d spin-polarized electrons through heterostructure design.« less
Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J. -W.; Choi, Y.; Chun, S. H.

Here, the combination of strong electron correlations in 3d transition metal oxides and spin-orbit interactions in the 5d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIrO 3 (SIO) and La 2/3Sr 1/3MnO 3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolvedmore » x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular-orbitals between the Mn and Ir layers modifying the Ir 5d electronic configuration through the mixture of t 2g and e g states, resulting in a deviation from J eff = ½. This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5d states with 2-dimensional 3d spin-polarized electrons through heterostructure design.« less
Polarized single crystal neutron diffraction study of the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x =0.024 )

NASA Astrophysics Data System (ADS)

Chatterji, T.; Stunault, A.; Brown, P. J.

2018-02-01

We have determined the temperature evolution of the spin and orbital moments in the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x = 0.024) by combining polarized and unpolarized single crystal neutron diffraction data. The sensitivity of the polarized neutron technique has allowed the moment values to be determined with a precision of ≈0.1 μB . Our results clearly demonstrate that, when magnetized by a field of 8 T, the spin and orbital moments in Sm1 -xGdxAl2 are oppositely directed, so that the net magnetization is very small. Below 60 K the contributions from spin and orbital motions are both about 2 μB , with that due to orbital motion being slightly larger than that due to spin. Between 60 and 65 K the contributions of each to the magnetization fall rapidly and change sign at Tcomp ≈67 K , above which the aligned moments recover but with the orbital magnetization still slightly higher than the spin one. These results imply that above Tcomp the small resultant magnetization of the Sm3 + ion is oppositely directed to the magnetizing field. It is suggested that this anomaly is due to polarization of conduction electron spin associated with the doping Gd3 + ions.
Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

NASA Astrophysics Data System (ADS)

Kim, J.-W.; Choi, Y.; Chun, S. H.; Haskel, D.; Yi, D.; Ramesh, R.; Liu, J.; Ryan, P. J.

2018-03-01

The combination of strong electron correlations in 3 d transition-metal oxides and spin-orbit interactions in the 5 d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIr O3 (SIO) and L a2 /3S r1 /3Mn O3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolved x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular orbitals between the Mn and Ir layers modifying the Ir 5 d electronic configuration through the mixture of t2 g and eg states, resulting in a deviation from Jeff=1 /2 . This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5 d states with two-dimensional 3 d spin-polarized electrons through heterostructure design.
NASA Tech Briefs, December 2013

NASA Technical Reports Server (NTRS)

2013-01-01

Topics include: Microwave Kinetic Inductance Detector With; Selective Polarization Coupling; Flexible Microstrip Circuits for; Superconducting Electronics; CFD Extraction Tool for TecPlot From DPLR Solutions; RECOVIR Software for Identifying Viruses; Enhanced Contact Graph Routing (ECGR) MACHETE Simulation Model; Orbital Debris Engineering Model (ORDEM) v.3; Scatter-Reducing Sounding Filtration Using a Genetic Algorithm and Mean Monthly Standard Deviation; Thermo-Mechanical Methodology for Stabilizing Shape Memory Alloy Response; Hermetic Seal Designs for Sample Return Sample Tubes; Silicon Alignment Pins: An Easy Way To Realize a Wafer-to-Wafer Alignment; Positive-Buoyancy Rover for Under Ice Mobility; Electric Machine With Boosted Inductance to Stabilize Current Control; International Space Station-Based Electromagnetic Launcher for Space Science Payloads; Advanced Hybrid Spacesuit Concept Featuring Integrated Open Loop and Closed Loop Ventilation Systems; Data Quality Screening Service.
Aqueous Assembly of Oxide and Fluoride Nanoparticles into 3D Microassemblies.

PubMed

Cui, Shanying; Guan, Xin N; Ghantous, Eliana; Vajo, John J; Lucas, Matthew; Hsiao, Ming-Siao; Drummy, Lawrence F; Collins, Joshua; Juhl, Abigail; Roper, Christopher S; Gross, Adam F

2018-06-28

We demonstrate rapid [∼mm 3 /(h·L)] organic ligand-free self-assembly of three-dimensional, >50 μm single-domain microassemblies containing up to 10 7 individual aligned nanoparticles through a scalable aqueous process. Organization and alignment of aqueous solution-dispersed nanoparticles are induced by decreasing their pH-dependent surface charge without organic ligands, which could be temperature-sensitive or infrared light absorbing. This process is exhibited by transforming both dispersed iron oxide hydroxide nanorods and lithium yttrium fluoride nanoparticles into high packing density microassemblies. The approach is generalizable to nanomaterials with pH-dependent surface charge (e.g., oxides, fluorides, and sulfides) for applications requiring long-range alignment of nanostructures as well as high packing density.
A Method for the Alignment of Heterogeneous Macromolecules from Electron Microscopy

PubMed Central

Shatsky, Maxim; Hall, Richard J.; Brenner, Steven E.; Glaeser, Robert M.

2009-01-01

We propose a feature-based image alignment method for single-particle electron microscopy that is able to accommodate various similarity scoring functions while efficiently sampling the two-dimensional transformational space. We use this image alignment method to evaluate the performance of a scoring function that is based on the Mutual Information (MI) of two images rather than one that is based on the cross-correlation function. We show that alignment using MI for the scoring function has far less model-dependent bias than is found with cross-correlation based alignment. We also demonstrate that MI improves the alignment of some types of heterogeneous data, provided that the signal to noise ratio is relatively high. These results indicate, therefore, that use of MI as the scoring function is well suited for the alignment of class-averages computed from single particle images. Our method is tested on data from three model structures and one real dataset. PMID:19166941
Space Technology 5 Multi-Point Observations of Temporal Variability of Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, Guan; Wang, Yongli; Slavin, James A.; Strangeway, Robert J.

2008-01-01

Space Technology 5 (ST5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that meso-scale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of approximately 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are approximately 1 min for meso-scale currents and approximately 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.
Space Technology 5 (ST-5) Observations of Field-Aligned Currents: Temporal Variability

NASA Technical Reports Server (NTRS)

Le, Guan

2010-01-01

Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from STS. The data demonstrate that masoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about I min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.
Space Technology 5 Multi-point Observations of Field-aligned Currents: Temporal Variability of Meso-Scale Structures

NASA Technical Reports Server (NTRS)

Le, Guan; Wang, Yongli; Slavin, James A.; Strangeway, Robert J.

2007-01-01

Space Technology 5 (ST5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that meso-scale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of - 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are approx. 1 min for meso-scale currents and approx. 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.
Space Technology 5 (ST-5) Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, Guan

2010-01-01

Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that mesoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about 1 min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.
Effective one body approach to the dynamics of two spinning black holes with next-to-leading order spin-orbit coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Damour, Thibault; Jaranowski, Piotr; Schaefer, Gerhard

2008-07-15

Using a recent, novel Hamiltonian formulation of the gravitational interaction of spinning binaries, we extend the effective one body (EOB) description of the dynamics of two spinning black holes to next-to-leading order (NLO) in the spin-orbit interaction. The spin-dependent EOB Hamiltonian is constructed from four main ingredients: (i) a transformation between the 'effective' Hamiltonian and the 'real' one; (ii) a generalized effective Hamilton-Jacobi equation involving higher powers of the momenta; (iii) a Kerr-type effective metric (with Pade-resummed coefficients) which depends on the choice of some basic 'effective spin vector' S{sub eff}, and which is deformed by comparable-mass effects; and (iv)more » an additional effective spin-orbit interaction term involving another spin vector {sigma}. As a first application of the new, NLO spin-dependent EOB Hamiltonian, we compute the binding energy of circular orbits (for parallel spins) as a function of the orbital frequency, and of the spin parameters. We also study the characteristics of the last stable circular orbit: binding energy, orbital frequency, and the corresponding dimensionless spin parameter a{sub LSO}{identical_to}cJ{sub LSO}/(G(H{sub LSO}/c{sup 2}){sup 2}). We find that the inclusion of NLO spin-orbit terms has a significant 'moderating' effect on the dynamical characteristics of the circular orbits for large and parallel spins.« less
Dynamics of Flexible MLI-type Debris for Accurate Orbit Prediction

DTIC Science & Technology

2014-09-01

sets usually are classical orbital elements , or Keplerian elements illustrated in Fig. 3. Fig. 3. Orbital elements ... elements in Table 2, for 10 orbits . Orbit of the objects is simulated by equation (3.9) and set the initial equation in Table 2. Gravitational...depending upon the parameters selected and the orbit to be propagated. For this reason, other sets of elements were defined and used in the

Comparison of Low Earth Orbit and Geosynchronous Earth Orbits

NASA Technical Reports Server (NTRS)

Drummond, J. E.

1980-01-01

The technological, environmental, social, and political ramifications of low Earth orbits as compared to geosynchronous Earth orbits for the solar power satellite (SPS) are assessed. The capital cost of the transmitting facilities is dependent on the areas of the antenna and rectenna relative to the requirement of high efficiency power transmission. The salient features of a low orbit Earth orbits are discussed in terms of cost reduction efforts.
An MHD simulation of By-dependent magnetospheric convection and field-aligned currents during northward IMF

NASA Technical Reports Server (NTRS)

Ogino, T.; Walker, R. J.; Ashour-Abdalla, M.; Dawson, J. M.

1985-01-01

A three-dimensional MHD simulation code is used to model the magnetospheric configuration when the IMF has both a northward B(z) component and a B(y) component in the east-west direction. Projections of the plasma pressure, the field-aligned velocity, the field-aligned vorticity, and the field-aligned current along the magnetic field lines into the northern ionosphere are shown and discussed. Cross-sectional patterns of these parameters are shown. The results demonstrate that the B(y) component of the IMF strongly influences the plasma sheet configuration and the magnetospheric convection pattern.
Collision energy dependent cross section and rotational alignment of NO (A 2Σ+) in the energy-transfer reaction of N2 (A 3Σu+) + NO (X 2Π) → N2 (X 1Σg+) + NO (A 2Σ+).

PubMed

Ohoyama, H

2014-10-16

We have studied the collision energy dependent cross section and alignment of NO (A (2)Σ(+)) rotation in the energy-transfer reaction of N2 (A (3)Σ(u)(+)) + NO (X (2)Π) → N2 (X (1)Σ(g)(+)) + NO (A (2)Σ(+)) at the collision energy (E) region of 0.03-0.2 eV. NO (A (2)Σ(+)) emission in two linear polarization directions in the collision frame (parallel (∥) and perpendicular (⊥) with respect to the relative velocity vector (vR)) has been measured as a function of collision energy. NO (A (2)Σ(+)) rotation (J-vector) turns out to be aligned perpendicular to vR. In addition, collision energy is found to enhance the degree of alignment of NO (A (2)Σ(+)) rotation. The collision energy dependent cross sections σ(∥,(⊥))(E) (excitation functions) show a rapid fall-off following an initial rise with a threshold less than 0.02 eV. The excitation function at the parallel alignment of NO (A (2)Σ(+)) rotation, σ(J∥v(R), (E), is slightly shifted to the low collision energy region as compared with σ(J ⊥ vR, E). We propose that the rapid fall-off feature in the excitation function is attributed to the multidimensional nonadiabatic transitions.
Spin Evolution of Stellar Progenitors in Compact Binaries

NASA Astrophysics Data System (ADS)

Steinle, Nathan; Kesden, Michael

2018-01-01

Understanding the effects of various processes on the spins of stellar progenitors in compact binary systems is important for modeling the binary’s evolution and thus for interpreting the gravitational radiation emitted during inspiral and merger. Tides, winds, and natal kicks can drastically modify the binary parameters: tidal interactions increase the spin magnitudes, align the spins with the orbital angular momentum, and circularize the orbit; stellar winds decrease the spin magnitudes and cause mass loss; and natal kicks can misalign the spins and orbital angular momentum or even disrupt the binary. Also, during Roche lobe overflow, the binary may experience either stable mass transfer or common envelope evolution. The former can lead to a mass ratio reversal and alter the component spins, while the latter can dramatically shrink the binary separation. For a wide range of physically reasonable stellar-evolution scenarios, we compare the timescales of these processes to assess their relative contributions in determining the initial spins of compact binary systems.
Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

DOE PAGES

Pullen, M. G.; Wolter, B.; Le, A. -T.; ...

2016-06-22

The ability to directly follow and time-resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser-induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as pg) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval ofmore » the structure of randomly oriented O 2 and C 2H 2 molecules, with π g and π u symmetries, respectively, and where their ionization probabilities do not maximize along their molecular axes. As a result, while this removes a serious bottleneck for laser-induced diffraction imaging, we find unexpectedly strong backscattering contributions from low-Z atoms.« less
Effects of finite coverage on global polarization observables in heavy ion collisions

NASA Astrophysics Data System (ADS)

Lan, Shaowei; Lin, Zi-Wei; Shi, Shusu; Sun, Xu

2018-05-01

In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented polarization signals for Λ hyperons and possible spin alignment signals for ϕ mesons. Here we discuss the effects of finite coverage on these observables. The results from a multi-phase transport and a toy model both indicate that a pseudorapidity coverage narrower than | η | < ∼ 1 will generate a larger value for the extracted ϕ-meson ρ00 parameter; thus a finite coverage can lead to an artificial deviation of ρ00 from 1/3. We also show that a finite η and pT coverage affect the extracted pH parameter for Λ hyperons when the real pH value is non-zero. Therefore proper corrections are necessary to reliably quantify the global polarization with experimental observables.
ILLUMINATING BLACK HOLE BINARY FORMATION CHANNELS WITH SPINS IN ADVANCED LIGO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Carl L.; Zevin, Michael; Pankow, Chris

The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary evolution in galactic fields and dynamical formation in dense star clusters, the predicted masses and merger rates overlap significantly, complicating any astrophysical claims that rely on measured masses alone. Here, we examine the distribution of spin–orbit misalignments expected for binaries from the field and from dense star clusters. Under standard assumptions for black hole natal kicks, we find that black hole binaries similar to GW150914 couldmore » be formed with significant spin–orbit misalignment only through dynamical processes. In particular, these heavy-black hole binaries can only form with a significant spin–orbit anti -alignment in the dynamical channel. Our results suggest that future detections of merging black hole binaries with measurable spins will allow us to identify the main formation channel for these systems.« less
A 5 Micron of beta Pictoris B at a Sub-Jupiter Projected Separation: Evidence for a Misalignment Between the Planet and the Inner, Warped Disk

NASA Technical Reports Server (NTRS)

Currie, Thayne; Thalmann, Christian; Matsumura, Soko; Madhusudhan, Nikku; Burrows, Adam; Kuchner, Marc

2011-01-01

We present and analyze a new M' detection of the young exoplanet Beta Pictoris b from 2008 VLT/NaCo data at a separation of approx. = 4 AU and a high signal-to-noise rereduction of L' data taken in December 2Q09. Based on our orbital analysis, the planet's orbit is viewed almost perfectly edge-on (i approx. 89 degrees) and has a Saturn-like semimajor axis of 9.50AU(+3.93 AU)/-(1.7AU) . Intriguingly, the planet's orbit is aligned with the major axis of the outer disk (Omega approx.31 degrees) but probably misaligned with the warp/inclined disk at 80 AU often cited as a signpost for the planet's existence. Our results motivate new studies to clarify how Beta Pic b sculpts debris disk structures and whether a second planet is required to explain the warp/inclined disk
Zigzag nanoribbons of two-dimensional silicene-like crystals: magnetic, topological and thermoelectric properties.

PubMed

Wierzbicki, Michał; Barnaś, Józef; Swirkowicz, Renata

2015-12-09

The effects of electron-electron and spin-orbit interactions on the ground-state magnetic configuration and on the corresponding thermoelectric and spin thermoelectric properties in zigzag nanoribbons of two-dimensional hexagonal crystals are analysed theoretically. The thermoelectric properties of quasi-stable magnetic states are also considered. Of particular interest is the influence of Coulomb and spin-orbit interactions on the topological edge states and on the transition between the topological insulator and conventional gap insulator states. It is shown that the interplay of both interactions also has a significant impact on the transport and thermoelectric characteristics of the nanoribbons. The spin-orbit interaction also determines the in-plane magnetic easy axis. The thermoelectric properties of nanoribbons with in-plane magnetic moments are compared to those of nanoribbons with edge magnetic moments oriented perpendicularly to their plane. Nanoribbons with ferromagnetic alignment of the edge moments are shown to reveal spin thermoelectricity in addition to the conventional one.
The Microscope Space Mission and the In-Orbit Calibration Plan for its Instrument

NASA Astrophysics Data System (ADS)

Levy, Agnès Touboul, Pierre; Rodrigues, Manuel; Onera, Émilie Hardy; Métris, Gilles; Robert, Alain

2015-01-01

The MICROSCOPE space mission aims at testing the Equivalence Principle (EP) with an accuracy of 10-15. This principle is one of the basis of the General Relativity theory; it states the equivalence between gravitational and inertial mass. The test is based on the precise measurement of a gravitational signal by a differential electrostatic accelerometer which includes two cylindrical test masses made of different materials. The accelerometers constitute the payload accommodated on board a drag-free micro-satellite which is controlled inertial or rotating about the normal to the orbital plane. The acceleration estimates used for the EP test are disturbed by the instruments physical parameters and by the instrument environment conditions on-board the satellite. These parameters are partially measured with ground tests or during the integration of the instrument in the satellite (alignment). Nevertheless, the ground evaluations are not sufficient with respect to the EP test accuracy objectives. An in-orbit calibration is therefore needed to characterize them finely. The calibration process for each parameter has been defined.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Beauge, C.; Nesvorny, D.

Doppler and transit observations of exoplanets show a pile-up of Jupiter-size planets in orbits with a 3 day period. A fraction of these hot Jupiters have retrograde orbits with respect to the parent star's rotation, as evidenced by the measurements of the Rossiter-McLaughlin effect. To explain these observations we performed a series of numerical integrations of planet scattering followed by the tidal circularization and migration of planets that evolved into highly eccentric orbits. We considered planetary systems having three and four planets initially placed in successive mean-motion resonances, although the angles were taken randomly to ensure orbital instability in shortmore » timescales. The simulations included the tidal and relativistic effects, and precession due to stellar oblateness. Our results show the formation of two distinct populations of hot Jupiters. The inner population (Population I) is characterized by semimajor axis a < 0.03 AU and mainly formed in the systems where no planetary ejections occurred. Our follow-up integrations showed that this population was transient, with most planets falling inside the Roche radius of the star in <1 Gyr. The outer population of hot Jupiters (Population II) formed in systems where at least one planet was ejected into interstellar space. This population survives the effects of tides over >1 Gyr and fits nicely the observed 3 day pile-up. A comparison between our three-planet and four-planet runs shows that the formation of hot Jupiters is more likely in systems with more initial planets. Due to the large-scale chaoticity that dominates the evolution, high eccentricities and/or high inclinations are generated mainly by close encounters between the planets and not by secular perturbations (Kozai or otherwise). The relative proportion of retrograde planets seems of be dependent on the stellar age. Both the distribution of almost aligned systems and the simulated 3 day pile-up also fit observations better in our four-planet simulations. This may suggest that the planetary systems with observed hot Jupiters were originally rich in the number of planets, some of which were ejected. In a broad perspective, our work therefore hints on an unexpected link between the hot Jupiters and recently discovered free floating planets.« less
Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals.

PubMed

Liu, Qingkun; Tang, Jianwei; Zhang, Yuan; Martinez, Angel; Wang, Shaowei; He, Sailing; White, Timothy J; Smalyukh, Ivan I

2014-05-01

We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.
NuSTAR: system engineering and modeling challenges in pointing reconstruction for a deployable x-ray telescope

NASA Astrophysics Data System (ADS)

Harp, D. Isaiah; Liebe, Carl Christian; Craig, William; Harrison, Fiona; Kruse-Madsen, Kristin; Zoglauer, Andreas

2010-07-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will make the first sensitive images of the sky in the high energy X-ray band (6 - 80 keV). The NuSTAR observatory consists of two co-aligned grazing incidence hard X-ray telescopes with a ~10 meter focal length, achieved by the on-orbit extension of a deployable mast. A principal science objective of the mission is to locate previously unknown high-energy X-ray sources to an accuracy of 10 arcseconds (3-sigma), sufficient to uniquely identify counterparts at other wavelengths. In order to achieve this, a star tracker and laser metrology system are an integral part of the instrument; in conjunction, they will determine the orientation of the optics bench in celestial coordinates and also measure the flexures in the deployable mast as it responds to the varying on-orbit thermal environment, as well as aerodynamic and control torques. The architecture of the NuSTAR system for solving the attitude and aspect problems differs from that of previous X-ray telescopes, which did not require ex post facto reconstruction of the instantaneous observatory alignment on-orbit. In this paper we describe the NuSTAR instrument metrology system architecture and implementation, focusing on the systems engineering challenges associated with validating the instantaneous transformations between focal plane and celestial coordinates to within the required accuracy. We present a mathematical solution to photon source reconstruction, along with a detailed error budget that relates component errors to science performance. We also describe the architecture of the instrument simulation software being used to validate the end-to-end performance model.
RAVAN CubeSat Results: Technologies and Science Demonstrated On Orbit

NASA Astrophysics Data System (ADS)

Swartz, W. H.; Lorentz, S. R.; Huang, P. M.; Smith, A. W.; Yu, Y.; Briscoe, J. S.; Reilly, N.; Reilly, S.; Reynolds, E.; Carvo, J.; Wu, D.

2017-12-01

Elucidating Earth's energy budget is vital to understanding and predicting climate, particularly the small imbalance between the incident solar irradiance and Earth-leaving fluxes of total and solar-reflected energy. Accurately quantifying the spatial and temporal variation of Earth's outgoing energy from space is a challenge—one potentially rendered more tractable with the advent of multipoint measurements from small satellite or hosted payload constellations. The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) 3U CubeSat, launched November 11, 2016, is a pathfinder for a constellation to measure the Earth's energy imbalance. The objective of RAVAN is to establish that compact, broadband radiometers absolutely calibrated to high accuracy can be built and operated in space for low cost. RAVAN demonstrates two key technologies: (1) vertically aligned carbon nanotubes as spectrally flat radiometer absorbers and (2) gallium phase-change cells for on-board calibration and degradation monitoring of RAVAN's radiometer sensors. We show on-orbit results, including calibrated irradiance measurements at both shortwave, solar-reflected wavelengths and in the thermal infrared. These results are compared with both modeled upwelling fluxes and those measured by independent Earth energy instruments in low-Earth orbit. Further, we show the performance of two gallium phase-change cells that are used to monitor the degradation of RAVAN's radiometer sensors. In addition to Earth energy budget technology and science, RAVAN also demonstrates partnering with a commercial vendor for the CubeSat bus, payload integration and test, and mission operations. We conclude with a discussion of how a RAVAN-type constellation could enable a breakthrough in the measurement of Earth's energy budget and lead to superior predictions of future climate.
Suomi NPP VIIRS solar diffuser screen transmittance model and its applications.

PubMed

Lei, Ning; Xiong, Xiaoxiong; Mcintire, Jeff

2017-11-01

The visible infrared imaging radiometer suite on the Suomi National Polar-orbiting Partnership satellite calibrates its reflective solar bands through observations of a sunlit solar diffuser (SD) panel. Sunlight passes through a perforated plate, referred to as the SD screen, before reaching the SD. It is critical to know whether the SD screen transmittance measured prelaunch is accurate. Several factors such as misalignments of the SD panel and the measurement apparatus could lead to errors in the measured transmittance and thus adversely impact on-orbit calibration quality through the SD. We develop a mathematical model to describe the transmittance as a function of the angles that incident light makes with the SD screen, and apply the model to fit the prelaunch measured transmittance. The results reveal that the model does not reproduce the measured transmittance unless the size of the apertures in the SD screen is quite different from the design value. We attribute the difference to the orientation alignment errors for the SD panel and the measurement apparatus. We model the alignment errors and apply our transmittance model to fit the prelaunch transmittance to retrieve the "true" transmittance. To use this model correctly, we also examine the finite source size effect on the transmittance. Furthermore, we compare the product of the retrieved "true" transmittance and the prelaunch SD bidirectional reflectance distribution function (BRDF) value to the value derived from on-orbit data to determine whether the prelaunch SD BRDF value is relatively accurate. The model is significant in that it can evaluate whether the SD screen transmittance measured prelaunch is accurate and help retrieve the true transmittance from the transmittance with measurement errors, consequently resulting in a more accurate sensor data product by the same amount.
A Scanning Hartmann Focus Test for the EUVI Telescopes aboard STEREO

NASA Technical Reports Server (NTRS)

Ohl, Ray; Antonille, Scott; Aronstein, Dave; Dean, Bruce; Eichhorn, Bil; Frey, Brad; Kubalak, Dave; Shiri, Ron; Smith, Scott; Wilson, Mark;

2007-01-01

The Solar TErrestrial RElations Observatory (STEREO), the third mission in NASA's Solar Terrestrial Probes program, was launched in 2006 on a two year mission to study solar phenomena. STEREO consists of two nearly identical satellites, each carrying an Extreme Ultraviolet Imager (EUVI) telescope as part of the Sun Earth Connection Coronal and Heliospheric Investigation instrument suite. EUVI is a normal incidence, 98mm diameter, Ritchey-Chretien telescope designed to obtain wide field of view images of the Sun at short wavelengths (17.1-30.4nm) using a CCD detector. The telescope entrance aperture is divided into four quadrants by a mask near the secondary mirror spider veins. A mechanism that rotates another mask allows only one of these sub-apertures to accept light over an exposure. The EUVI contains no focus mechanism. Mechanical models predict a difference in telescope focus between ambient integration conditions and on-orbit operation. We describe an independent check of the ambient, ultraviolet, absolute focus setting of the EUVI telescopes after they were integrated with their respective spacecraft. A scanning Hartmann-like test design resulted from constraints implied by the EUVI aperture select mechanism. This inexpensive test was simultaneously coordinated with other NASA integration and test activities in a high-vibration, clean room environment. The total focus test error was required to be better than +/-0.05 mm. We describe the alignment and test procedure, sources of statistical and systematic error, and then the focus determination results using various algorithms. The results are consistent with other tests of focus alignment and indicate that the EUVI telescopes meet the ambient focus offset requirements. STEREO is functioning well on-orbit and the EUVI telescopes meet their on-orbit image quality requirements.

Focus adjustment method for CBERS 3 and 4 satellites Mux camera to be performed in air condition and its experimental verification for best performance in orbital vacuum condition

NASA Astrophysics Data System (ADS)

Scaduto, Lucimara C. N.; Malavolta, Alexandre T.; Modugno, Rodrigo G.; Vales, Luiz F.; Carvalho, Erica G.; Evangelista, Sérgio; Stefani, Mario A.; de Castro Neto, Jarbas C.

2017-11-01

The first Brazilian remote sensing multispectral camera (MUX) is currently under development at Opto Eletronica S.A. It consists of a four-spectral-band sensor covering a 450nm to 890nm wavelength range. This camera will provide images within a 20m ground resolution at nadir. The MUX camera is part of the payload of the upcoming Sino-Brazilian satellites CBERS 3&4 (China-Brazil Earth Resource Satellite). The preliminary alignment between the optical system and the CCD sensor, which is located at the focal plane assembly, was obtained in air condition, clean room environment. A collimator was used for the performance evaluation of the camera. The preliminary performance evaluation of the optical channel was registered by compensating the collimator focus position due to changes in the test environment, as an air-to-vacuum environment transition leads to a defocus process in this camera. Therefore, it is necessary to confirm that the alignment of the camera must always be attained ensuring that its best performance is reached for an orbital vacuum condition. For this reason and as a further step on the development process, the MUX camera Qualification Model was tested and evaluated inside a thermo-vacuum chamber and submitted to an as-orbit vacuum environment. In this study, the influence of temperature fields was neglected. This paper reports on the performance evaluation and discusses the results for this camera when operating within those mentioned test conditions. The overall optical tests and results show that the "in air" adjustment method was suitable to be performed, as a critical activity, to guarantee the equipment according to its design requirements.
Report on orbital debris

NASA Technical Reports Server (NTRS)

1989-01-01

The success of space endeavors depends upon a space environment sufficiently free of debris to enable the safe and dependable operation of spacecraft. An environment overly cluttered with debris would threaten the ability to utilize space for a wide variety of scientific, technological, military, and commercial purposes. Man made space debris (orbital debris) differs from natural meteoroids because it remains in earth orbit during its lifetime and is not transient through the space around the Earth. The orbital debris environment is considered. The space environment is described along with sources of orbital debris. The current national space policy is examined, along with ways to minimize debris generation and ways to survive the debris environment. International efforts, legal issues and commercial regulations are also examined.
Increased alignment sensitivity improves the usage of genome alignments for comparative gene annotation.

PubMed

Sharma, Virag; Hiller, Michael

2017-08-21

Genome alignments provide a powerful basis to transfer gene annotations from a well-annotated reference genome to many other aligned genomes. The completeness of these annotations crucially depends on the sensitivity of the underlying genome alignment. Here, we investigated the impact of the genome alignment parameters and found that parameters with a higher sensitivity allow the detection of thousands of novel alignments between orthologous exons that have been missed before. In particular, comparisons between species separated by an evolutionary distance of >0.75 substitutions per neutral site, like human and other non-placental vertebrates, benefit from increased sensitivity. To systematically test if increased sensitivity improves comparative gene annotations, we built a multiple alignment of 144 vertebrate genomes and used this alignment to map human genes to the other 143 vertebrates with CESAR. We found that higher alignment sensitivity substantially improves the completeness of comparative gene annotations by adding on average 2382 and 7440 novel exons and 117 and 317 novel genes for mammalian and non-mammalian species, respectively. Our results suggest a more sensitive alignment strategy that should generally be used for genome alignments between distantly-related species. Our 144-vertebrate genome alignment and the comparative gene annotations (https://bds.mpi-cbg.de/hillerlab/144VertebrateAlignment_CESAR/) are a valuable resource for comparative genomics. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.
Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites

NASA Astrophysics Data System (ADS)

Wells, Brian; Kumar, Raj; Reynolds, C. Lewis; Peters, Kara; Bradford, Philip D.

2017-12-01

Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies >400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/- oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites.

Rashba spin-orbit coupling and orbital chirality in magnetic bilayers

NASA Astrophysics Data System (ADS)

Lee, Hyun-Woo

2013-03-01

The phenomenon of the Rashba spin-orbit coupling is examined theoretically for an ultrathin magnetic layer in contact with a non-magnetic heavy metal layer. From first-principles calculation, large Rashba parameter of order 1 eV .Å is obtained, which is strong enough to generate large spin transfer torque of spin-orbit coupling origin. Large Rashba parameter is attributed to the orbital mixing of 3 d magnetic atoms and non-magnetic heavy elements with significant atomic spin-orbit coupling. Interestingly the magnitude and sign of the parameter vary from energy bands to bands, which we attribute to band-specific chiral ordering of orbital angular momentum. Through a simple tight-binding model analysis, we demonstrate that d-orbital hybridization allowed by the breaking of structural inversion symmetry generates band-specific chiral ordering of orbital angular momentum, which combines with atomic spin-orbit coupling to give rise to band-specific Rashba parameter. The band-dependence of the Rashba parameter is discussed in connection with recent experiments and we argue that the dependence may be utilized to enhance device application potentials. This work is supported by NRF grant (2010-0008529, 2011-0015631, 2010-0014109, 2011-0030789).
Optical tools and techniques for aligning solar payloads with the SPARCS control system. [Solar Pointing Aerobee Rocket Control System

NASA Technical Reports Server (NTRS)

Thomas, N. L.; Chisel, D. M.

1976-01-01

The success of a rocket-borne experiment depends not only on the pointing of the attitude control system, but on the alignment of the attitude control system to the payload. To ensure proper alignment, special optical tools and alignment techniques are required. Those that were used in the SPARCS program are described and discussed herein. These tools include theodolites, autocollimators, a 38-cm diameter solar simulator, a high-performance 1-m heliostat to provide a stable solar source during the integration of the rocket payload, a portable 75-cm sun tracker for use at the launch site, and an innovation called the Solar Alignment Prism. Using the real sun as the primary reference under field conditions, the Solar Alignment Prism facilitates the coalignment of the attitude sun sensor with the payload. The alignment techniques were developed to ensure the precise alignment of the solar payloads to the SPARCS attitude sensors during payload integration and to verify the required alignment under field conditions just prior to launch.
Nature of the water/aromatic parallel alignment interactions.

PubMed

Mitoraj, Mariusz P; Janjić, Goran V; Medaković, Vesna B; Veljković, Dušan Ž; Michalak, Artur; Zarić, Snežana D; Milčić, Miloš K

2015-01-30

The water/aromatic parallel alignment interactions are interactions where the water molecule or one of its O-H bonds is parallel to the aromatic ring plane. The calculated energies of the interactions are significant, up to ΔE(CCSD)(T)(limit) = -2.45 kcal mol(-1) at large horizontal displacement, out of benzene ring and CH bond region. These interactions are stronger than CH···O water/benzene interactions, but weaker than OH···π interactions. To investigate the nature of water/aromatic parallel alignment interactions, energy decomposition methods, symmetry-adapted perturbation theory, and extended transition state-natural orbitals for chemical valence (NOCV), were used. The calculations have shown that, for the complexes at large horizontal displacements, major contribution to interaction energy comes from electrostatic interactions between monomers, and for the complexes at small horizontal displacements, dispersion interactions are dominant binding force. The NOCV-based analysis has shown that in structures with strong interaction energies charge transfer of the type π → σ*(O-H) between the monomers also exists. © 2014 Wiley Periodicals, Inc.
Phonon-drag magnetothermopower in Rashba spin-split two-dimensional electron systems.

PubMed

Biswas, Tutul; Ghosh, Tarun Kanti

2013-10-16

We study the phonon-drag contribution to the thermoelectric power in a quasi-two-dimensional electron system confined in GaAs/AlGaAs heterostructure in the presence of both Rashba spin-orbit interaction and perpendicular magnetic field at very low temperature. It is observed that the peaks in the phonon-drag thermopower split into two when the Rashba spin-orbit coupling constant is strong. This splitting is a direct consequence of the Rashba spin-orbit interaction. We show the dependence of phonon-drag thermopower on both magnetic field and temperature numerically. A power-law dependence of phonon-drag magnetothermopower on the temperature in the Bloch-Gruneisen regime is found. We also extract the exponent of the temperature dependence of phonon-drag thermopower for different parameters like electron density, magnetic field, and the spin-orbit coupling constant.
On the period of the periodic orbits of the restricted three body problem

NASA Astrophysics Data System (ADS)

Perdomo, Oscar

2017-09-01

We will show that the period T of a closed orbit of the planar circular restricted three body problem (viewed on rotating coordinates) depends on the region it encloses. Roughly speaking, we show that, 2 T=kπ +\\int _Ω g where k is an integer, Ω is the region enclosed by the periodic orbit and g:R^2→ R is a function that only depends on the constant C known as the Jacobian constant; it does not depend on Ω . This theorem has a Keplerian flavor in the sense that it relates the period with the space "swept" by the orbit. As an application we prove that there is a neighborhood around L_4 such that every periodic solution contained in this neighborhood must move clockwise. The same result holds true for L_5.
Earth orbital teleoperator visual system evaluation program

NASA Technical Reports Server (NTRS)

Frederick, P. N.; Shields, N. L., Jr.; Kirkpatrick, M., III

1977-01-01

Visual system parameters and stereoptic television component geometries were evaluated for optimum viewing. The accuracy of operator range estimation using a Fresnell stereo television system with a three dimensional cursor was examined. An operator's ability to align three dimensional targets using vidicon tube and solid state television cameras as part of a Fresnell stereoptic system was evaluated. An operator's ability to discriminate between varied color samples viewed with a color television system was determined.
Spacecraft Optical Contamination Environment

DTIC Science & Technology

1989-04-01

is imaging mode with filer slider; mniddle is Fabry-Perot configuration; bottom Is imaging spectrometer 14 4.0 FLIGHT OPERATIONS PLANNING A flight... planning meeting was held at Johnson Space Center on the 22nd of March,1989. This meeting was attended by Drs. C. Pike and Edmond Murad from AFGL and Dr...3 exposures for each thruster firing planned during this period of Orbiter darkness. View Angle: Spectrograph slit to be aligned with centerline of
Comparison of ring-focus image profile with predictions for the AXAF VETA-I test

NASA Technical Reports Server (NTRS)

Zissa, David E.

1993-01-01

The X-ray test of the largest pair of nearly cylindrical mirrors for the Advanced X-ray Astrophysics Facility (AXAF) was completed in October 1991 at Marshall Space Flight Center. The test assembly was named the Verification Engineering Test Article I (VETA-I). The ring-focus portion of the test measured the imaging quality of azimuthal sections of VETA-I. This gives information about the core of the on-orbit image. The finite source distance, VETA-I mirror spacing, and VETA-I structural deformation caused the core of the image to be spread over a diameter of nearly 4 arc seconds at the VETA-I overall focus. The results of a preliminary analysis of the ring-focus data and the implications for the on-orbit image of the telescope are discussed. An upper limit for the on-orbit encircled-energy fraction at 1 arc second diameter was determined to be 0.82 at 0.277 keV X-ray energy. This assumes that the bottoms of the mirrors in the VETA-I arrangement are representative of the mirror surfaces and that the on-orbit system would be aligned using a combination of preliminary measurements and predictions for the mirror surface shapes.
Alignment of CH3F in para-H2 crystal studied by IR quantum cascade laser polarization spectroscopy.

PubMed

Kawasaki, Hiroyuki; Mizoguchi, Asao; Kanamori, Hideto

2016-05-14

In order to investigate the alignment of CH3F in para-H2 crystals, high resolution polarization spectroscopy of the ν3 vibrational band is studied using a quantum cascade laser at 1040 cm(-1). It is found that the main and satellite series of peaks in the ν3 vibrational band of CH3F have the same polarization dependence. This result supports the previously proposed cluster model with ortho-H2 in first and second nearest neighbor sites. The observed polarization dependence function is well described by a simple six-axis void model in which CH3F is not aligned along the c-axis of the crystal but tilted to 64.9(3)° from it.
Fast localized orthonormal virtual orbitals which depend smoothly on nuclear coordinates.

PubMed

Subotnik, Joseph E; Dutoi, Anthony D; Head-Gordon, Martin

2005-09-15

We present here an algorithm for computing stable, well-defined localized orthonormal virtual orbitals which depend smoothly on nuclear coordinates. The algorithm is very fast, limited only by diagonalization of two matrices with dimension the size of the number of virtual orbitals. Furthermore, we require no more than quadratic (in the number of electrons) storage. The basic premise behind our algorithm is that one can decompose any given atomic-orbital (AO) vector space as a minimal basis space (which includes the occupied and valence virtual spaces) and a hard-virtual (HV) space (which includes everything else). The valence virtual space localizes easily with standard methods, while the hard-virtual space is constructed to be atom centered and automatically local. The orbitals presented here may be computed almost as quickly as projecting the AO basis onto the virtual space and are almost as local (according to orbital variance), while our orbitals are orthonormal (rather than redundant and nonorthogonal). We expect this algorithm to find use in local-correlation methods.
Nonlocal correlations in the orbital selective Mott phase of a one-dimensional multiorbital Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, S.; Kaushal, N.; Wang, Y.

Here, we study nonlocal correlations in a three-orbital Hubbard model defined on an extended one-dimensional chain using determinant quantum Monte Carlo and density matrix renormalization group methods. We focus on a parameter regime with robust Hund's coupling, which produces an orbital selective Mott phase (OSMP) at intermediate values of the Hubbard U, as well as an orbitally ordered ferromagnetic insulating state at stronger coupling. An examination of the orbital- and spin-correlation functions indicates that the orbital ordering occurs before the onset of magnetic correlations in this parameter regime as a function of temperature. In the OSMP, we find that themore » self-energy for the itinerant electrons is momentum dependent, indicating a degree of nonlocal correlations while the localized electrons have largely momentum independent self-energies. These nonlocal correlations also produce relative shifts of the holelike and electronlike bands within our model. The overall momentum dependence of these quantities is strongly suppressed in the orbitally ordered insulating phase.« less
Nonlocal correlations in the orbital selective Mott phase of a one-dimensional multiorbital Hubbard model

DOE PAGES

Li, S.; Kaushal, N.; Wang, Y.; ...

2016-12-12

Here, we study nonlocal correlations in a three-orbital Hubbard model defined on an extended one-dimensional chain using determinant quantum Monte Carlo and density matrix renormalization group methods. We focus on a parameter regime with robust Hund's coupling, which produces an orbital selective Mott phase (OSMP) at intermediate values of the Hubbard U, as well as an orbitally ordered ferromagnetic insulating state at stronger coupling. An examination of the orbital- and spin-correlation functions indicates that the orbital ordering occurs before the onset of magnetic correlations in this parameter regime as a function of temperature. In the OSMP, we find that themore » self-energy for the itinerant electrons is momentum dependent, indicating a degree of nonlocal correlations while the localized electrons have largely momentum independent self-energies. These nonlocal correlations also produce relative shifts of the holelike and electronlike bands within our model. The overall momentum dependence of these quantities is strongly suppressed in the orbitally ordered insulating phase.« less
* Fabrication and Characterization of Biphasic Silk Fibroin Scaffolds for Tendon/Ligament-to-Bone Tissue Engineering.

PubMed

Font Tellado, Sònia; Bonani, Walter; Balmayor, Elizabeth R; Foehr, Peter; Motta, Antonella; Migliaresi, Claudio; van Griensven, Martijn

2017-08-01

Tissue engineering is an attractive strategy for tendon/ligament-to-bone interface repair. The structure and extracellular matrix composition of the interface are complex and allow for a gradual mechanical stress transfer between tendons/ligaments and bone. Thus, scaffolds mimicking the structural features of the native interface may be able to better support functional tissue regeneration. In this study, we fabricated biphasic silk fibroin scaffolds designed to mimic the gradient in collagen molecule alignment present at the interface. The scaffolds had two different pore alignments: anisotropic at the tendon/ligament side and isotropic at the bone side. Total porosity ranged from 50% to 80% and the majority of pores (80-90%) were <100-300 μm. Young's modulus varied from 689 to 1322 kPa depending on the type of construct. In addition, human adipose-derived mesenchymal stem cells were cultured on the scaffolds to evaluate the effect of pore morphology on cell proliferation and gene expression. Biphasic scaffolds supported cell attachment and influenced cytoskeleton organization depending on pore alignment. In addition, the gene expression of tendon/ligament, enthesis, and cartilage markers significantly changed depending on pore alignment in each region of the scaffolds. In conclusion, the biphasic scaffolds fabricated in this study show promising features for tendon/ligament-to-bone tissue engineering.
On the long-period evolution of the sun-synchronous orbits

NASA Astrophysics Data System (ADS)

Kuznetsov, E. D.; Jasim, A. T.

2016-05-01

The dynamic evolution of sun-synchronous orbits at a time interval of 20 years is considered. The numerical motion simulation has been carried out using the Celestial Mechanics software package developed at the Institute of Astronomy of the University of Bern. The dependence of the dynamic evolution on the initial value of the ascending node longitude is examined for two families of sun-synchronous orbits with altitudes of 751 and 1191 km. Variations of the semimajor axis and orbit inclination are obtained depending on the initial value of the ascending node longitude. Recommendations on the selection of orbits, in which spent sun-synchronous satellites can be moved, are formulated. Minimal changes of elements over a time interval of 20 years have been observed for orbits in which at the initial time the angle between the orbit ascending node and the direction of the Sun measured along the equator have been close to 90° or 270°. In this case, the semimajor axis of the orbit is not experiencing secular perturbations arising from the satellite's passage through the Earth's shadow.
Curvature-induced microswarming and clustering of self-propelled particles

NASA Astrophysics Data System (ADS)

Bruss, Isaac; Glotzer, Sharon

Non-equilibrium active matter systems exhibit many unique phenomena, such as motility-induced phase separation and swarming. However, little is known about how these behaviors depend on the geometry of the environment. To answer this question, we use Brownian dynamics simulations to study the effects of Gaussian curvature on self-propelled particles by confining them to the surface of a sphere. We find that a modest amount of curvature promotes phase separation by altering the shape of a cluster's boundary. Alternatively, particles on surfaces of high curvature experience reduced phase separation and instead form microswarms, where particles share a common orbit. We show that this novel flocking behavior is distinct from other previously studied examples, in that it is not explicitly incorporated into our model through Vicsek-like alignment rules nor torques. Rather, we find that microswarms emerge solely due to the geometric link between orientation and velocity, a property exclusive to surfaces with non-zero Gaussian curvature. These findings reveal the important role of local environment on the global emergent behavior of non-equilibrium systems. Center for Bio-Inspired Engineering (DOE Award # DE-SC0000989).
Dissociative double-photoionization of butadiene in the 25-45 eV energy range using 3-D multi-coincidence ion momentum imaging spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oghbaie, Shabnam; Gisselbrecht, Mathieu; Laksman, Joakim

Dissociative double-photoionization of butadiene in the 25-45 eV energy range has been studied with tunable synchrotron radiation using full three-dimensional ion momentum imaging. Using ab initio calculations, the electronic states of the molecular dication below 33 eV are identified. The results of the measurement and calculation show that double ionization from π orbitals selectively triggers twisting about the terminal or central C–C bonds. We show that this conformational rearrangement depends upon the dication electronic state, which effectively acts as a gateway for the dissociation reaction pathway. For photon energies above 33 eV, three-body dissociation channels where neutral H-atom evaporation precedesmore » C–C charge-separation in the dication species appear in the correlation map. The fragment angular distributions support a model where the dication species is initially aligned with the molecular backbone parallel to the polarization vector of the light, indicating a high probability for double-ionization to the “gateway states” for molecules with this orientation.« less
James Webb Space Telescope Orbit Determination Analysis

NASA Technical Reports Server (NTRS)

Yoon, Sungpil; Rosales, Jose; Richon, Karen

2014-01-01

The James Webb Space Telescope (JWST) is designed to study and answer fundamental astrophysical questions from an orbit about the Sun-Earth/Moon L2 libration point, 1.5 million km away from Earth. This paper describes the results of an orbit determination (OD) analysis of the JWST mission emphasizing the challenges specific to this mission in various mission phases. Three mid-course correction (MCC) maneuvers during launch and early orbit phase and transfer orbit phase are required for the spacecraft to reach L2. These three MCC maneuvers are MCC-1a at Launch+12 hours, MCC-1b at L+2.5 days and MCC-2 at L+30 days. Accurate OD solutions are needed to support MCC maneuver planning. A preliminary analysis shows that OD performance with the given assumptions is adequate to support MCC maneuver planning. During the nominal science operations phase, the mission requires better than 2 cm/sec velocity estimation performance to support stationkeeping maneuver planning. The major challenge to accurate JWST OD during the nominal science phase results from the unusually large solar radiation pressure force acting on the huge sunshield. Other challenges are stationkeeping maneuvers at 21-day intervals to keep JWST in orbit around L2, frequent attitude reorientations to align the JWST telescope with its targets and frequent maneuvers to unload momentum accumulated in the reaction wheels. Monte Carlo analysis shows that the proposed OD approach can produce solutions that meet the mission requirements.
Description and User Instructions for the Quaternion_to_Orbit_v3 Software

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry V.; Kruizinga, Gerhard L.; Paik, Meegyeong; Yuan, Dah-Ning; Asmar, Sami W.

2012-01-01

For a given inertial frame of reference, the software combines the spacecraft orbits with the spacecraft attitude quaternions, and rotates the body-fixed reference frame of a particular spacecraft to the inertial reference frame. The conversion assumes that the two spacecraft are aligned with respect to the mutual line of sight, with a parameterized time tag. The software is implemented in Python and is completely open source. It is very versatile, and may be applied under various circumstances and for other related purposes. Based on the solid linear algebra analysis, it has an extra option for compensating the linear pitch. This software has been designed for simulation of the calibration maneuvers performed by the two spacecraft comprising the GRAIL mission to the Moon, but has potential use for other applications. In simulations of formation flights, one needs to coordinate the spacecraft orbits represented in an appropriate inertial reference frame and the spacecraft attitudes. The latter are usually given as the time series of quaternions rotating the body-fixed reference frame of a particular spacecraft to the inertial reference frame. It is often desirable to simulate the same maneuver for different segments of the orbit. It is also useful to study various maneuvers that could be performed at the same orbit segment. These two lines of study are more timeand labor-efficient if the attitude and orbit data are generated independently, so that the part of the data that has not been changed can be recycled in the course of multiple simulations.
Synchronization of finite-size particles by a traveling wave in a cylindrical flow

NASA Astrophysics Data System (ADS)

Melnikov, D. E.; Pushkin, D. O.; Shevtsova, V. M.

2013-09-01

Motion of small finite-size particles suspended in a cylindrical thermocapillary flow with an azimuthally traveling wave is studied experimentally and numerically. At certain flow regimes the particles spontaneously align in dynamic accumulation structures (PAS) of spiral shape. We find that long-time trajectories of individual particles in this flow fall into three basic categories that can be described, borrowing the dynamical systems terminology, as the stable periodic, the quasiperiodic, and the quasistable periodic orbits. Besides these basic types of orbits, we observe the "doubled" periodic orbits and shuttle-like particle trajectories. We find that ensembles of particles having periodic orbits give rise to one-dimensional spiral PAS, while ensembles of particles having quasiperiodic orbits form two-dimensional PAS of toroidal shape. We expound the reasons why these types of orbits and the emergence of the corresponding accumulation structures should naturally be anticipated based on the phase locking theory of PAS formation. We give a further discussion of PAS features, such as the finite thickness of PAS spirals and the probable scenarios of the spiral PAS destruction. Finally, in numerical simulations of inertial particles we observe formation of the spiral structures corresponding to the 3:1 "resonance" between the particle turnover frequency and the wave oscillations frequency, thus confirming another prediction of the phase locking theory. In view of the generality of the arguments involved, we expect the importance of this structure-forming mechanism to go far beyond the realm of the laboratory-friendly thermocapillary flows.
Impurities in Antiferromagnetic Transition-Metal Oxides - Symmetry and Optical Transitions

NASA Astrophysics Data System (ADS)

Petersen, John Emil, III

The study of antiferromagnetic transition-metal oxides is an extremely active area in the physical sciences, where condensed matter physics, inorganic chemistry, and materials science blend together. The sheer number of potential commercial applications is staggering, but much of the fundamental science remains unexplained. This is not due to a lack of effort, however, as theorists have been struggling to understand these materials for decades - particularly the character of the band edges and first optical transitions. The difficulty lies in the strong correlation or Coloumb attraction between the electrons in the anisotropic d orbitals, which conventional band theory cannot describe adequately. The correlation problem is approached here by the well-accepted method of adding a Hubbard potential energy term to the ground state Hamiltonian, calculated within Density Functional Theory. The frequency-dependent complex dielectric function is calculated within the Independent Particle Approximation, and optical transitions are evaluated in multiple different ways. Peaks in the imaginary part of the dielectric function are compared energetically to orbitally decomposed density of states calculations. Optical transitions are typically analyzed in terms of atomic orbitals, which, strictly speaking, gives misleading results. Here, however, from the calculated data, two alternative interpretations are analyzed for each material studied. The first employs rigorous group theoretical analysis to determine allowed electric-dipole transitions, taking into account both orbital hybridization and crystal symmetry. The second interpretation is that of metal cation site hopping. In this interpretation, carriers hop from the x2 - y2 d orbital of one metal cation lattice site to the next metal cation site which is antiferromagnetically aligned. At times, thoughout this work, one interpretation is favorable to the other. Which interpretation is most valid depends on the material considered. For example, simple rock-salt transition-metal oxides are quite different from the high temperature superconducting cuprates. A range of materials is studied here, in order to gain a greater understanding of optical transitions in highly-correlated systems. In this work, O vacancies are introduced in NiO, along with Fe impurities, to understand better the band filling in the insulating behavior observed experimentally. These results are compared with those of La2NiO4, La2CuO4, La2-xSr xNiO4, and La2-xSrxCuO4. to elucidate the mechanisms behind the symmetry breaking phenomena in the Sr doped systems. As it turns out, indeed, the x2 - y2 orbital in these materials plays a critical role in spatial charge distribution, magnetic, and spin densities which are coupled to the dopant position in the lattice. The in-depth study of electronic and optical properties of transition-metal oxides presented here provides theoretical characterization of the infamous pseudogap in the cuprates - one of the greatest mysteries of modern solid state physics. In addition, via Density Functional Perturbation Theory, the phonon coupling with charge-density wave is explored in La2-xSr xNiO4 and found to be the dominant contributing factor to the colossal dielectric constant.

Binary star formation: gravitational fragmentation followed by capture

NASA Astrophysics Data System (ADS)

Turner, J. A.; Chapman, S. J.; Bhattal, A. S.; Disney, M. J.; Pongracic, H.; Whitworth, A. P.

1995-11-01

We describe in detail one of a sequence of numerical simulations which realize the mechanism of binary star formation proposed by Pringle. In these simulations, collisions between stable molecular cloud clumps produce dense shocked layers, which cool radiatively and fragment gravitationally. The resulting fragments then condense to form protostellar discs, which at the same time fall together and, as a result of tidal and viscous interactions, capture one another to form binary systems. We refer to this mechanism as shock-induced gravitational fragmentation followed by capture, or SGF+C. When the initial clumps are sufficiently massive and/or the Mach number of the collision is sufficiently high, a large number (>~10) of protostellar discs is produced; under these circumstances, the layer fragments first into filaments, and then into beads along the filaments. The marriage of two protostellar discs in this way is `arranged' in the sense that the protostellar discs involved do not form independently. First, they both condense out of the same layer, and probably also out of the same filament within this layer; this significantly increases the likelihood of them interacting dynamically. Secondly, there tends to be alignment between the orbital and spin angular momenta of the interacting protostellar discs, reflecting the fact that these angular momenta derive mainly from the systematic global angular momentum of the off-axis collision which produced the layer; this alignment of the various angular momenta pre-disposes the discs to very dissipative interactions, thereby increasing the probability of producing a strongly bound, long-lasting union. It is a marriage because the binary orbit stabilizes itself rather quickly. Any subsequent orbit evolution, as the protostellar discs `mop up' the surrounding residual gas and interact tidally, tends to harden the orbit. Therefore, as long as a third body does not intervene, the union is binding. Even if a third body does intervene, provided the binary components are well matched (i.e. of comparable mass) and the third body is not too massive, such interventions will - more often than not - harden the orbit further. In two appendices we describe the code used in the simulations presented in this and the companion paper, and the tests performed to demonstrate the code's ability to handle the physical processes involved.
A Kinematic Link Between Boxy Bulges, Stellar Bars, and Nuclear Activity in NGC 3079 and NGC 4388

NASA Technical Reports Server (NTRS)

Veilleux, S.; Bland-Hawthrorn, J.; Cecil, Gerald

1999-01-01

We present direct kinematic evidence for bar streaming in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. In NGC 3079, bar streaming motions with moderately eccentric orbits (e = b/a approx. 0.7) aligned along PA = 130 deg. intrinsic to the disk (PA = 97 deg. on the sky) are detected out to R(sub b) = 3.6 kpc. The orbits become increasingly circular beyond that radius (e = 1 at R(sub d) approx. = 6 kpc). The best model for NGC 4388 includes highly eccentric orbits (e approx. 0.3) for R(sub) less than or equal to 1.5 kpc which are aligned along PA = 135 deg. intrinsic to the disk (PA = 100 deg. on the sky). The observed "spiral arms" are produced by having the orbits become increasingly circular from the ends of the bar to the edge of the disk (R(sub d) approx. = 5 kpc), and the intrinsic bar PA shifting from 135 deg. to 90 deg.. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity.
Size Dependence of S-bonding on (111) Facets of Cu Nanoclusters

DOE PAGES

Boschen, Jeffery S.; Lee, Jiyoung; Windus, Theresa L.; ...

2016-04-21

We demonstrate a strong damped oscillatory size dependence of the adsorption energy for sulfur on the (111) facets of tetrahedral Cu nanoclusters up to sizes of ~300 atoms. This behavior reflects quantum size effects. Consistent results are obtained from density functional theory analyses utilizing either atomic orbital or plane-wave bases and using the same Perdew–Burke–Ernzerhof functional. Behavior is interpreted via molecular orbitals (MO), density of states (DOS), and crystal orbital Hamilton population (COHP) analyses.
A geometric model of a V-slit Sun sensor correcting for spacecraft wobble

NASA Technical Reports Server (NTRS)

Mcmartin, W. P.; Gambhir, S. S.

1994-01-01

A V-Slit sun sensor is body-mounted on a spin-stabilized spacecraft. During injection from a parking or transfer orbit to some final orbit, the spacecraft may not be dynamically balanced. This may result in wobble about the spacecraft spin axis as the spin axis may not be aligned with the spacecraft's axis of symmetry. While the widely used models in Spacecraft Attitude Determination and Control, edited by Wertz, correct for separation, elevation, and azimuthal mounting biases, spacecraft wobble is not taken into consideration. A geometric approach is used to develop a method for measurement of the sun angle which corrects for the magnitude and phase of spacecraft wobble. The algorithm was implemented using a set of standard mathematical routines for spherical geometry on a unit sphere.
NASA/MSFC ground experiment for large space structure control verification

NASA Technical Reports Server (NTRS)

Waites, H. B.; Seltzer, S. M.; Tollison, D. K.

1984-01-01

Marshall Space Flight Center has developed a facility in which closed loop control of Large Space Structures (LSS) can be demonstrated and verified. The main objective of the facility is to verify LSS control system techniques so that on orbit performance can be ensured. The facility consists of an LSS test article which is connected to a payload mounting system that provides control torque commands. It is attached to a base excitation system which will simulate disturbances most likely to occur for Orbiter and DOD payloads. A control computer will contain the calibration software, the reference system, the alignment procedures, the telemetry software, and the control algorithms. The total system will be suspended in such a fashion that LSS test article has the characteristics common to all LSS.
Error Budgets for the Exoplanet Starshade (exo-s) Probe-Class Mission Study

NASA Technical Reports Server (NTRS)

Shaklan, Stuart B.; Marchen, Luis; Cady, Eric; Ames, William; Lisman, P. Douglas; Martin, Stefan R.; Thomson, Mark; Regehr, Martin

2015-01-01

Exo-S is a probe-class mission study that includes the Dedicated mission, a 30 millimeters starshade co-launched with a 1.1 millimeter commercial telescope in an Earth-leading deep-space orbit, and the Rendezvous mission, a 34 millimeter starshade intended to work with a 2.4 millimeters telescope in an Earth-Sun L2 orbit. A third design, referred to as the Rendezvous Earth Finder mission, is based on a 40 millimeter starshade and is currently under study. This paper presents error budgets for the detection of Earth-like planets with each of these missions. The budgets include manufacture and deployment tolerances, the allowed thermal fluctuations and dynamic motions, formation flying alignment requirements, surface and edge reflectivity requirements, and the allowed transmission due to micrometeoroid damage.
Detecting chaos, determining the dimensions of tori and predicting slow diffusion in Fermi-Pasta-Ulam lattices by the Generalized Alignment Index method

NASA Astrophysics Data System (ADS)

Skokos, C.; Bountis, T.; Antonopoulos, C.

2008-12-01

The recently introduced GALI method is used for rapidly detecting chaos, determining the dimensionality of regular motion and predicting slow diffusion in multi-dimensional Hamiltonian systems. We propose an efficient computation of the GALIk indices, which represent volume elements of k randomly chosen deviation vectors from a given orbit, based on the Singular Value Decomposition (SVD) algorithm. We obtain theoretically and verify numerically asymptotic estimates of GALIs long-time behavior in the case of regular orbits lying on low-dimensional tori. The GALIk indices are applied to rapidly detect chaotic oscillations, identify low-dimensional tori of Fermi-Pasta-Ulam (FPU) lattices at low energies and predict weak diffusion away from quasiperiodic motion, long before it is actually observed in the oscillations.
Error budgets for the Exoplanet Starshade (Exo-S) probe-class mission study

NASA Astrophysics Data System (ADS)

Shaklan, Stuart B.; Marchen, Luis; Cady, Eric; Ames, William; Lisman, P. Douglas; Martin, Stefan R.; Thomson, Mark; Regehr, Martin

2015-09-01

Exo-S is a probe-class mission study that includes the Dedicated mission, a 30 m starshade co-launched with a 1.1 m commercial telescope in an Earth-leading deep-space orbit, and the Rendezvous mission, a 34 m starshade intended to work with a 2.4 m telescope in an Earth-Sun L2 orbit. A third design, referred to as the Rendezvous Earth Finder mission, is based on a 40 m starshade and is currently under study. This paper presents error budgets for the detection of Earth-like planets with each of these missions. The budgets include manufacture and deployment tolerances, the allowed thermal fluctuations and dynamic motions, formation flying alignment requirements, surface and edge reflectivity requirements, and the allowed transmission due to micrometeoroid damage.
Dancing Twins: Stellar Hierarchies That Formed Sequentially?

NASA Astrophysics Data System (ADS)

Tokovinin, Andrei

2018-04-01

This paper draws attention to the class of resolved triple stars with moderate ratios of inner and outer periods (possibly in a mean motion resonance) and nearly circular, mutually aligned orbits. Moreover, stars in the inner pair are twins with almost identical masses, while the mass sum of the inner pair is comparable to the mass of the outer component. Such systems could be formed either sequentially (inside-out) by disk fragmentation with subsequent accretion and migration, or by a cascade hierarchical fragmentation of a rotating cloud. Orbits of the outer and inner subsystems are computed or updated in four such hierarchies: LHS 1070 (GJ 2005, periods 77.6 and 17.25 years), HIP 9497 (80 and 14.4 years), HIP 25240 (1200 and 47.0 years), and HIP 78842 (131 and 10.5 years).
Determination of the spin orbit coupling and crystal field splitting in wurtzite InP by polarization resolved photoluminescence

NASA Astrophysics Data System (ADS)

Chauvin, Nicolas; Mavel, Amaury; Jaffal, Ali; Patriarche, Gilles; Gendry, Michel

2018-02-01

Excitation photoluminescence spectroscopy is usually used to extract the crystal field splitting (ΔCR) and spin orbit coupling (ΔSO) parameters of wurtzite (Wz) InP nanowires (NWs). However, the equations expressing the valence band splitting are symmetric with respect to these two parameters, and a choice ΔCR > ΔSO or ΔCR < ΔSO has to be taken into account in order to assign the numerical values. To solve this issue, polarization resolved micro-photoluminescence was performed on vertically aligned and untapered Wz InP NWs grown on silicon. The experimental results combined with a theoretical model and finite difference time domain calculations allow us to conclude that ΔCR > ΔSO in Wz InP.
Mobile and replicated alignment of arrays in data-parallel programs

NASA Technical Reports Server (NTRS)

Chatterjee, Siddhartha; Gilbert, John R.; Schreiber, Robert

1993-01-01

When a data-parallel language like FORTRAN 90 is compiled for a distributed-memory machine, aggregate data objects (such as arrays) are distributed across the processor memories. The mapping determines the amount of residual communication needed to bring operands of parallel operations into alignment with each other. A common approach is to break the mapping into two stages: first, an alignment that maps all the objects to an abstract template, and then a distribution that maps the template to the processors. We solve two facets of the problem of finding alignments that reduce residual communication: we determine alignments that vary in loops, and objects that should have replicated alignments. We show that loop-dependent mobile alignment is sometimes necessary for optimum performance, and we provide algorithms with which a compiler can determine good mobile alignments for objects within do loops. We also identify situations in which replicated alignment is either required by the program itself (via spread operations) or can be used to improve performance. We propose an algorithm based on network flow that determines which objects to replicate so as to minimize the total amount of broadcast communication in replication. This work on mobile and replicated alignment extends our earlier work on determining static alignment.
Orbit Software Suite

NASA Technical Reports Server (NTRS)

Osgood, Cathy; Williams, Kevin; Gentry, Philip; Brownfield, Dana; Hallstrom, John; Stuit, Tim

2012-01-01

Orbit Software Suite is used to support a variety of NASA/DM (Dependable Multiprocessor) mission planning and analysis activities on the IPS (Intrusion Prevention System) platform. The suite of Orbit software tools (Orbit Design and Orbit Dynamics) resides on IPS/Linux workstations, and is used to perform mission design and analysis tasks corresponding to trajectory/ launch window, rendezvous, and proximity operations flight segments. A list of tools in Orbit Software Suite represents tool versions established during/after the Equipment Rehost-3 Project.
The fate of scattered planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

2014-12-01

As gas giant planets evolve, they may scatter other planets far from their original orbits to produce hot Jupiters or rogue planets that are not gravitationally bound to any star. Here, we consider planets cast out to large orbital distances on eccentric, bound orbits through a gaseous disk. With simple numerical models, we show that super-Earths can interact with the gas through dynamical friction to settle in the remote outer regions of a planetary system. Outcomes depend on planet mass, the initial scattered orbit, and the evolution of the time-dependent disk. Efficient orbital damping by dynamical friction requires planets atmore » least as massive as the Earth. More massive, longer-lived disks damp eccentricities more efficiently than less massive, short-lived ones. Transition disks with an expanding inner cavity can circularize orbits at larger distances than disks that experience a global (homologous) decay in surface density. Thus, orbits of remote planets may reveal the evolutionary history of their primordial gas disks. A remote planet with an orbital distance ∼100 AU from the Sun is plausible and might explain correlations in the orbital parameters of several distant trans-Neptunian objects.« less
Around Marshall

NASA Image and Video Library

1997-10-31

The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the sun's energy and use the energy for inexpensive space Propulsion Research. Pictured is an engineering model (Pathfinder III) of the Shooting Star Experiment (SSE). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflections of the engineering model under extreme conditions, such as the coldness of deep space and the hotness of the sun as well as vacuum. This thermal vacuum test was performed at the X-Ray Calibration Facility because of the size of the test article and the capabilities of the facility to simulate in-orbit conditions
Shooting Star Experiment

NASA Technical Reports Server (NTRS)

1997-01-01

The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the sun's energy and use the energy for inexpensive space Propulsion Research. Pictured is an engineering model (Pathfinder III) of the Shooting Star Experiment (SSE). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflections of the engineering model under extreme conditions, such as the coldness of deep space and the hotness of the sun as well as vacuum. This thermal vacuum test was performed at the X-Ray Calibration Facility because of the size of the test article and the capabilities of the facility to simulate in-orbit conditions
Design and realization of the optical and electron beam alignment system for the HUST-FEL oscillator

NASA Astrophysics Data System (ADS)

Fu, Q.; Tan, P.; Liu, K. F.; Qin, B.; Liu, X.

2018-06-01

A Free Electron Laser(FEL) oscillator with radiation wavelength at 30-100 μ m is under commissioning at Huazhong University of Science and Technology (HUST). This work presents the schematic design and realization procedures for the optical and beam alignment system in the HUST FEL facility. The optical cavity misalignment effects are analyzed with the code OPC + Genesis 1.3, and the tolerance of misalignment is proposed with the simulation result. Depending on undulator mechanical benchmarks, a laser indicating system has been built up as reference datum. The alignment of both optical axis and beam trajectory were achieved by this alignment system.
Intrinsic alignments of galaxies in the EAGLE and cosmo-OWLS simulations

NASA Astrophysics Data System (ADS)

Velliscig, Marco; Cacciato, Marcello; Schaye, Joop; Hoekstra, Henk; Bower, Richard G.; Crain, Robert A.; van Daalen, Marcel P.; Furlong, Michelle; McCarthy, I. G.; Schaller, Matthieu; Theuns, Tom

2015-12-01

We report results for the alignments of galaxies in the EAGLE and cosmo-OWLS hydrodynamical cosmological simulations as a function of galaxy separation (-1 ≤ log10(r/[ h-1 Mpc]) ≤ 2) and halo mass (10.7 ≤ log10(M200/[h-1 M⊙]) ≤ 15). We focus on two classes of alignments: the orientations of galaxies with respect to either the directions to, or the orientations of, surrounding galaxies. We find that the strength of the alignment is a strongly decreasing function of the distance between galaxies. For galaxies hosted by the most massive haloes in our simulations the alignment can remain significant up to ˜100 Mpc. Galaxies hosted by more massive haloes show stronger alignment. At a fixed halo mass, more aspherical or prolate galaxies exhibit stronger alignments. The spatial distribution of satellites is anisotropic and significantly aligned with the major axis of the main host halo. The major axes of satellite galaxies, when all stars are considered, are preferentially aligned towards the centre of the main host halo. The predicted projected direction-orientation alignment, ɛg+(rp), is in broad agreement with recent observations. We find that the orientation-orientation alignment is weaker than the orientation-direction alignment on all scales. Overall, the strength of galaxy alignments depends strongly on the subset of stars that are used to measure the orientations of galaxies and it is always weaker than the alignment of dark matter haloes. Thus, alignment models that use halo orientation as a direct proxy for galaxy orientation overestimate the impact of intrinsic galaxy alignments.
Clustalnet: the joining of Clustal and CORBA.

PubMed

Campagne, F

2000-07-01

Performing sequence alignment operations from a different program than the original sequence alignment code, and/or through a network connection, is often required. Interactive alignment editors and large-scale biological data analysis are common examples where such a flexibility is important. Interoperability between the alignment engine and the client should be obtained regardless of the architectures and programming languages of the server and client. Clustalnet, a Clustal alignment CORBA server is described, which was developed on the basis of Clustalw. This server brings the robustness of the algorithms and implementations of Clustal to a new level of reuse. A Clustalnet server object can be accessed from a program, transparently through the network. We present interfaces to perform the alignment operations and to control these operations via immutable contexts. The interfaces that select the contexts do not depend on the nature of the operation to be performed, making the design modular. The IDL interfaces presented here are not specific to Clustal and can be implemented on top of different sequence alignment algorithm implementations.
Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Ying; Srivastava, A. K., E-mail: abhishek-srivastava-lu@yahoo.co.in; Chigrinov, V. G.

In this article, we reveal a theoretical and experimental illustration of the Ferroelectric liquid crystal (FLC) grating fabricated by mean of patterned alignment based on photo-alignment. The complexity related to the mismatching of the predefined alignment domains on the top and bottom substrate has been avoided by incorporating only one side photo aligned substrate while the other substrate does not have any alignment layer. Depending on the easy axis in the said alignment domains and the azimuth plane of the impinging polarized light, the diffracting element can be tuned in two modes i.e. DIFF/OFF switchable and DIFF/TRANS switchable modes, whichmore » can be applied to different applications. The diffraction profile has been illustrated theoretically that fits well with the experimental finding and thus the proposed diffraction elements with fast response time and high diffraction efficiency could find application in many modern devices.« less
Numerical simulation of large-scale field-aligned current generation from finite-amplitude magnetosonic waves

NASA Technical Reports Server (NTRS)

Yamauchi, M.

1994-01-01

A two-dimensional numerical simulation of finite-amplitude magnetohydrodynamic (MHD) magnetosonic waves is performed under a finite-velocity background convection condition. Isothermal cases are considered for simplicity. External dissipation is introduced by assuming that the field-aligned currents are generated in proportion to the accumulated charges. The simulation results are as follows: Paired field-aligned currents are found from the simulated waves. The flow directions of these field-aligned currents depend on the angle between the background convection and the wave normal, and hence two pairs of field-aligned currents are found from a bowed wave if we look at the overall structure. The majority of these field-aligned currents are closed within each pair rather than between two wings. These features are not observed under slow background convection. The result could be applied to the cusp current system and the substorm current system.

Some links on this page may take you to non-federal websites. Their policies may differ from this site.